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MG MGB Technical - Reason for too thick oil?
| When I dismantled my MGB engine, I was surpised to see how black and thick the oil was that was left in the bottom of the sump and the oil cooler. I always change the oil fairly frequently. Yesterday, I read in a motoring magazine that SAAB are having problems with some engines in their current 9-5 and 9-3 models. The trouble is that the oil is getting too thick in the engine, and the reason is believed to be exhaust gases that are going past the pistons and into the sump. Now that sounds familiar! Can anyone explain what the exhaust gases are doing to the oil? Just curious... Tore |
| Tore |
| Tore Firstly, oils will oxidise in time, and that oxidation forces a physical and chemical change in the oil. Essentially molecules are starting to form larger molecules as a result of the impurities and free radicals in the base stock reacting, which results in a higher viscosity, and acids are formed which cause the oil to become corrosive. In addition, solid deposits start to form in the oil that eventually migrate to the component surfaces and over time form sticky varnishs or hard carbonaceous deposits, but this very small material (<1µm) also causes a darkening of the oil, and with time will also create a foul odour like a rotten egg smell. This oxidation rate is controlled to an extent by the anti-oxidant package in the oil, but this does not last forever, and in reality merely slows down the oxidation rate. Other factors will influence the oxidation rate: heat, air, water and reactive metals associated with the wear debris and components. Heat is there in abundance, and based on the Arhenius Rule, the service life of a mineral oil is halved for every 10°C rise in temperature above 40°C. Exhaust fumes into the sump will also increase the temp. Water enters the oil either from condensation or from the combustion process itself - hence the exhaust fumes. In addition, because of the sulphur present in the fuel, this can react with the water to form sulphuric acid. In addition, the presence of water in the oil is either dissolved, or in a free or emulsified state depending on the saturation point. In an oil cooler, the Saturation point will be much lower so that condensation occurs and free water exists. In the sump the oil is hotter, but when the engine cools (esp. in Scandanavian Winter temps) the water condensates out. Hence cars used for short journeys never burn off the water (and other contaminants) from the sump properly and need more frequent oil changes. Air provides the oxygen necessary for oxidation - and any splashing can induce aeration in the oil. The oil normally has an anti-foamant to help disperse air bubbles quickly from the oil, otherwise aerated oil is fed to the high pressure zones and can cause cavitation damage. When I was lucky enough to meet Mario Andretti a few years back, he said that in the 70s Lotus F1 cars had a problem with cam failures, which related to a lack of defoamant in the oil. Lastly, wear debris material is ever present in the oil, as are the components. Copper is highly reactive (think batteries), and especially so in the presence of water. Again, oil will have corrosion inhibitors that coat the surfaces to protect the oil against the metals, as well as protecting the components against any accumulated acids in the oil. In the case of engines as opposed to other units like the diff or gearbox, the engine oil also has a problem of soot loading, esp. so on diesel engines. This will also cause discolouration of the oil. Diesel engines have a high particulate emission, and in the last few decades, diesel engines have been fitted with an Exhaust Gas Recirculation valve (EGR) and this forces any unburnt fuel in the exhaust gases back into the intake system, along with soot, and this increases the soot in the oil. A dispersancy additive is used to suspend the small soot particles at <0.1µm) to avoid them agglomerating and becoming abrasive, and this dispersancy is also alkaline to help neutralise acid formation. Modern oil formulations tend not to suffer these same oxidation problems in the highly refined Grp III mineral oils, or the synthetic Grp IV Polyalphaolefin basestocks, hence tehir longer service life amongst many other advantages. I hope that has answered your question. Martin |
| Martin ZT |
| Tore Gases get there past the rings as Saab say. That said, Saab get twice the power. Modern oils contain detergent. They should get black quickly as this shows they are holding the soot particles in suspension. If multigrade oil is not changed it goes through 2 stages. First it gets thinner as the thickening polymers break up and it reverts to its base oil viscosity. Then, if you leave it long enough, like my father in law, you find it starts thickening up due to excess carbon. Saab may be finding their turbo engines with extra heat is speeding up this process. I used a flushing oil at services in one I had and it came out like hot black parafin. Old spec oil, by comparison, stayed cleaner longer. They had no detergents and did not dissolve the carbon, which was left to sit in oilways and line the block and sump. Anyone who's worked on old engines will remember it can even go quite hard and scaley. It has been variously termed "black death" and "black sludge" and a later oil spec, SF or SG I think, is designed to address the problem which was highlighted with increasing numbers of OHC engines in the 80s. Rich |
| Rich |
| What you guys know... Thanks! |
| Tore |
| Oil will sludge over time in any traps that hold oil after all that can be drained out is drained out at each oil change. Both my sumps have the boss for the drain plug *inside* the sump and not outside, so there is always 1/4" to 1/2" of oil left in the bottom on draining. Same in some small pockets in the heads of the V8, even though the rest of the engine was a golden brown colour. |
| Paul Hunt |
| Rich My experience is that older oils got black from soot and sludge and oxidation issues. It used to be said with detergent oils that they should get black quickly as it is an indication the oil is doing its job. However, with modern oil formulations, it is not unusual for it not to discolour as quickly, simply because the issues of oxidation and sludging have been virtually eliminated. It will discolour with time with the build up of soot from the combustion chamber, but in modern petrol engines where the combustion is better controlled there is less soot creation. But these excellent quality oil formulations is why the likes of Audi and BMW offer 24k/2yr oil change intervals. Also, the newer oils don't need detergents as the synthetics themselves are detergent in action, and thus eliminate depositing on the component surfaces generally. Martin |
| Martin ZT |
| Martin By "Old spec oil, by comparison, stayed cleaner longer." I was referring to 60s oils, SA, SB, without detergent, they stayed cleaner than later ones with. By "Modern oils contain detergent. They should get black quickly as this shows they are holding the soot particles in suspension." I was referring to the 80s SF, SG, type mineral oils such as many of us use. Selected mineral and synthetics do stay cleaner for the reasons you say - in modern engines. This may not be the case with their use in older engines though and I'm not sure we can simply follow latest specs or think of our cars in terms of modern ones. Modern engines are designed and engineered to use very little oil if any between services and their fuelling and running conditions are tightly controlled. They help the oil compared with older engines and are in no way like a B engine. Timescale-wise they are like comparing a B engine with a Model T. For example, if they do not dirty the oil then the oil may not need so much detergent but our B engine still would. Another, they are fitted with cats which means excluding some additives which may be beneficial for our use. Oil technology has now passed our engines and we are in a position of having to choose the best oil rather than the latest spec. Motorcycle manufacturers stopped using car oils at the point of introduction of SJ spec for cats but we move on to new areas there. This is the reason for my "engine oil" thread which is throwing up some interesting thoughts. Rich |
| Rich |
| Thanks for the clarification, Rich. As you will see in your thread, I am using Mobil1 which I intend to closely monitor being in the lubrication business (not in an oil company though). In fairness, my engine is recently rebuilt. However, the oil has been slower to discolour than the cheaper 20W50 oils I was using in the running in period up to 3k miles. My other concern is finding a quality filter here in the UK - to me this is equally as important as the oil and fuel quality. What are your thoughts? Martin |
| Martin ZT |
| Rich But its the oil! Sludge is still a problem with a modern engine run on mineral. Raising the temperature of a molecule causes it to vibrate and rotate and if enough energy of the correct frequency is present, it will blow it apart. Mechanical shearing places shear-type stresses on the molecule and pressure in one or more directions can cause the molecule to separate at certain bonding sites. Synthetic oil molecules are stronger than petroleum molecules and thus are more "shear stable." Oxidation occurs when an oxygen molecule replaces one or more hydrogen or carbon bonding sites (usually due to increased temperatures acting as a catalyst), resulting in peroxides, causing sludge. Petroleum oils are less stable than are synthetics in this case. In most cases, and due to the geometry of the smaller oil hydrocarbon molecules, mechanical shearing is reversible; that is, once the shear stress (pressure) is relieved, there is enough coulombic (electrostatic energy) to help the ends find each other. There will always be a few molcules that do not find each other and remain sheared. Reagrding additives, the very large Viscosity Index Improving (VII) additive molecules are more prone to shearing than are oil molecules, mainly because of their molecular arrangement and size. VII molecules are "coiled" when cold and thus present very little resistance to movement (flow). When heated up, the VII molecules "un-coil" and are more resistant to flow, which is why VII's cause an oil to thicken when hot and, and thin when cold. VII molecules shear more easily under mechanical shearing forces (because they are larger) and are more prone to "permanent" shear, leaving the large unattached methacrylate molecules to thicken the oil over time. If heated and oxidized, these remnants also contribute to sludge. Synthetics are cleaner. Aw additives work in different areas and temperatures. Zinc low temp, moly high temp, Boron rings but the natural aw is esters Video presentation http://www.redlineoil.com/products_motoroil.asp?productID=53&synthFlash=1 M1 uses AN more than esters Castrol 15% of a unique ester developed in Germany! Silkolene Pro 20% Diester Motul 20% Diester and ester Redline ester Millers triple ester The lastest spec has the latest technology, Boron being fairly new as aw but IMO the base oil will be key. Redline 40wt is a 15W40, a 40weight oil which flows when cold. A mineral (oversimplified) a thin 15wt Oil with viscosity improvers and in view of above will be the main problem unless perfect engine conditions and then changed on a regular basis. As Martin mentioned minerals will start to use more GIII to improve product with a strong add pack. Some oil use may help keep rings clean and fuel dilution will be better handled by a Synthetic rather than mineral. Although the new requirements may be a concern, oil technology is moving on as well. Paul |
| Paul |
| Paul Some engines do break down the oil itself and need synthetic but they're mainly ones like turbos where there are areas of high heat and pressure. B engines dirty their oil with blow-bye gasses, unvapourised and part-burnt fuel. They take forever to warm through and run oil coolers without stats causing condensation, acid and corrosion. They produce little power and are little stressed. They have huge sumps with nearly twice the content of some cars. The oil gets dirty from the engine and the way to handle that is to keep it suspended, so it cannot settle, then change it regularly. I'm not keen on using flush as there's a lot left behind in the cooler. Much of what synthetic oil offers is wasted as our engines don't break down the oil itself to a degree that matters on short changes or need the extra film strength. There may be gains in cold start and economy depending on the ambient temp and type of running but many are too thin when cold and will not physically cushion the large clearances. Imho a good brand 20/50 SF or SG changed regularly gives the best of old and new for these engines. Martin Filtration raises a point which illustrates the above. Amsoil have shown it's possible to run 30,000 miles on synthetic. As you say, oil breakdown isn't the problem. What they have to do though, even using modern engines, is to use very fine bye-pass filtration to extract the bye-products of combustion including water. They also do their own fine filters for the standard full flow position for extended but lesser mileages. My first concern was to make sure there was even oil there at all on start-up! You guys pointed out the 18V filter holder could be fitted to my older engine, allowing a cartridge filter with a non-return valve. Filter is a Mann 916/1. The longest it's been left unstarted is a week and the pressure came up instantly so that was a good move. The information about micron filtration level etc is not available afaik but that part number is an OE quality filter made for our specific car rather than a generic type. I've also installed a magnetic sump bung from a seller on eBay which is well made though I've yet to see what it catches! http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=4534891847 Rich |
| Rich |
| Rich When the oil film is sheared or squeezed out, then your protection is now reliant on barrier lubricant additives. Oil has 3 states of lubrication , Hydrodynamic, mixed film, and boundary(barrier). The best is Hydrodynamic which is nothing more than a flow of oil separating two mating surfaces. After a period of time shearing, the oil will lose it's ability to hold up to the same flow as before since the VI Improvers are breaking down causing the oil to thin down in grade. Once this happens, there is less film strength between the mating surfaces so it doesn't take as much for the oil to shear, therefore creating more heat which attacks the base oil even more and then starts to cause the oil to thicken up due to the excessive levels of heat and the broken down VI Improvers become a contaminant which added to the existing oil will continue to thicken and ultimately cause sludge if not changed in a reasonable time. After the base oil has sheared or squeezed out, The last line of defense is an additive that puts down a barrier film. This additive (or ester) usually has higher levels of strength against shearing so it helps keep the wear down. Agreed that in 96 the lubrication industry changed from the SH to SJ API rated oil by reducing the barrier lubricant additives to help preserve cat converters on cars. However, this has led to the use of non-phosphorus AW EP additives such as MoTDC and the Borates. In addition there are esters most published by Castrol Magnatec http://www.silkoleneoil.com/techtip8.htm I do not understand your "thin" or "cushion" comment For start up protection flow esters and then additives prevent wear. Additives generally work at higher temperatures Offhand Zinc 60c and Moly may take 2 mins. http://www.luboron.com/EngineOilTreatment.shtml On start up your oil pressure will exceed relief valve pressure and therefore will bypass going to were its needed. When the piston is forced down from the explosion a lot of pressure is being applied through the upper rod bearing against the crank. When the piston is on the up stroke, the other pistons are pushing the crank around so there is no real pressure on the bottom there is very little wear against the bottom. Older engines with tappets with relatively high contact stresses that use up the antiwear additives in the oil, spur gear oil pumps that shear the oil viscosity down, distributor drive gears for the distributor and oil pump that shear the oil as well. PCV systems are often not nearly as efficient at purging the crank case. Carbs put much more fuel into the oil on cold starts. All of these factors shear the oil viscosity down faster in an older engine. Barry mentioned this oil, Delo 15-40 for diesel engines, the add pack is very strong, similar to M1, and IMO looks an excellant choice. However Synthetics with esters deal with all of the above better than any mineral oil and will deal with very high heat situations, the downside is that they are expensive but I consider them like any other performance part for the engine, but unlike most performace parts can repay/contribute to its additional cost. Paul |
| Paul |
| Paul, I think you are talking about Delo 400 15W-40 which is CI-4 plus for diesel engine. It has SL claim also. This oil has extremely high shear & oxidation stability, the detergency & dispersency is very high. People always find that after switching to this oil, the 1st or even the 2nd drain the oil would be very black which means the oil clean the sludge out. Then the 3rd, 4th....drained oil is very clear! But if the engine has not been properly maintained and was wore, it used more oil as the sludge sealed up the the valve guide..... was washed out! Ennio |
| Ennio Wong |
| Paul Look back to the 1967 BMC manual and we see monograde was specified for change at 3000 miles and multigrade at 6000. Multigrade has always been known to break down its thickening polymers and revert to its base viscosity so why should BMC say it could still last twice as long as monograde which doesn't suffer in this way? It suggests that oil break down wasn't the issue. Monogrades were largely without additives and the first additives combated corrosion, so it would seem contamination was the problem. That was 20W/40 SC in 1967 and oil's come a long way since then. By 1969 all 8 brand recommendations above -12°C were for 20W/50. By the 80s the SF version was getting 9000 mile changes in most other cars. Anyway, I'm quite happy with 20W/50 SG, it's still 10 years newer than the last B :-) Whatever you use get the correct viscosity. It's true that thinner oil flows easier when cold but these engines have large clearances when cold. The pistons in particular will rock and leak fuel and gases into the oil. Until they heat and expand they need thick oil to support and seal them. The oil pump is not like todays high delivery types, and splash lube will not stick as it's meant to. Using thin oil in a cold B is like running a knackered engine on thin oil - not a good thing. Rich |
| Rich |
| Rich A cold engine is an empty engine. On the assumption that an anti-drain back valve is working correctly, you still have to get the oil up to the working parts quickly, and get it flowing. 20W50 became the norm thanks to the Mini, so I was told by a trusted colleague that was 30 years in the industry. The gearbox in the sump chewed up the VII, and this, in combination with the propensity for the VII additives to shear, and get trapped in the filter lead to overspecifying the viscosity at hot operation on the basis the oil would start to work like a 20W40 after a few hours bedding in in the engine. Oil analysts commonly allow for a 10% drop in viscosity on used engine oil samples of only a few hours operation and research has proven this is simply permanent shear down of mineral multi-grades. The reason we see so much more 0w, 5W and 10W is that the synthetic has a naturally high VI not requiring VII, whereas mineral and to a lesser extent, semi-synths do, and their VI is lower. The temp and vis relationship is plotted as a straight line, but vis is a log plot, temp is a linear plot. Therefore a few °C change at low temps is a big change in cSt (or mm2/s in SI units). But a similar temp delta temp at operating temps is only a few cSt change. Therefore, a 0W is actually much thicker than the 50 rating, but way thinner than the 20W at the same cold start. Think of the VI as a ski slope on the graph passing through 40°C. A low VI means a steep slope, a high VI means a flatter slope - Ideally we want the slope as flat as possible, but that won't happen unless we use water. With respect to engine clearances, I know there is a discussion regarding bearing size and needing a thicker oil (although we mustn't confuse higher viscosity as a direct relationship with film strength). But the US have historically used 10W30 (although I believe as a compromise to avoiding bore polishing owing to piston design issues) which suggests that the clearances in their engines can tolerate lower SAE grades at running temperature. Having read an article by a US mechanic, he firmly believes that the tolerances are no different today than back in the 70s. Whether that is the case or not, a newly rebuilt engine is still going to be tight, and if I can utilise the synthetic from after the running -in phase, I believe this will have value (not everyone will see it this way, I accept) in allowing me to go the year or 6k miles without need for change. Fuel and water will burn off if the car is used for long enough periods (as opposed to short journeys). Acids may not, of course, so I would still revert to the good old blotter spot test to confirm the oil was up to scratch. |
| Martin ZT |
| US Old spec oil problem http://www.imakenews.com/lng/e_article000346479.cfm?x=b11,0,w Ennio Same problem as changing to Synthetic after long term mineral use. Auto rx is probably a safer and better way to clean an engine with these problems. "Piston Slap" can still be an issue with modern engines, a thick oil would only possibly muffle sound. "Shell global solutions" indicated a lower vis oil can actually give a thicker film re bores and if there is an issue flow and esters would still be best solution. http://www.imakenews.com/lng/e_article000346479.cfm?x=b11,0,w Paul |
| Paul |
| Both I've no arguement with synthetic being better in many respects and it's good to try and understand the technology in this hobby of ours and balance it with our own experience. Paul links to a story about SA oil and its interesting to put that grade in perspective and see how things have progressed, pinched from a site, "SA and SB oils were used in the early days, and had hardly any additives. One early chemist did suggest adding 0.1-0.2% red phosphorus to reduce oxidation, but nobody took much notice. In the 1920s, fatty acids were added to reduce friction, and to improve the "wetting" ability of the base oil. In the 1930s, anti-corrosion agents were added. In 1964, SC oils appeared. They had additives to protect against rust, and low-temperature sludge. In 1968, the SD oils had even more additives to protect against high- and low-temperature engine deposits, as well as wear, rust and corrosion. The SE oils in 1972 had more additives again, to protect the engine from deposits, sludge, wear, rust, and corrosion, and to protect the oil oil oxidising or burning. SF oils in 1980 had (you guessed it) even more additives, as did the SG oils in 1989. The additives increased from nearly zilcho in the SA and SB oils, to 7% by weight in the SE oils, to 25% in the SG oils! So when you buy 4 litres SG oil, 1 litre is all additives." So our B's came in with the very basic SB and stopped with SE. We don't know how the base oils and viis have changed but probably not worse. I ran them as daily drivers in the 70s, mostly Duckhams and Castrol SE without problems, and can now use SG. Rich |
| Rich |
| Rich MG subjects go from totally original to modified to extreme, all individual preference. How oil works is complex to the extreme. Martin is an oil consultant. full stop. More additives less oil! Synergy is key and application. However myths abound rather than fact, and we are all on a learning curve if we want to be. Like you I have been daily driving since 70s and Duckhams Castrol choice. The best way to test oil is engines off production line etc etc. Go with flow! Paul |
| Paul |
| Paul Let me ask you and Martin a question, If MG was still alive and well and making the B today, and Martin visited to discuss their oil requirements, what do you think they would end up specifying? Rich |
| Rich |
| Rich My view is the B should have developed into the British 911. Porsche have a minimum specification of a Group 3 synthetic and a number of other test protocols over A3-B3 in order to achieve Porsche Approval A minimum HTHS viscosity of 3.5 is required and the extra tests include foaming control and a minimum viscosity at 100C of 11cSt. They have an extended HTHS test protocol (and a special regime at 100C). Their factory fill is M1 0w-40 has been for years. Paul |
| Paul |
| That's a politician's answer Paul ;-) TVR beat BMC to it so let's try again. It's 2005 and the B has developed along our traditional lines. It offers the same 95 brake engine and box as the late 60's models and radial tyres are standard as is a radio and new checkered seat fabric. It now has 2 cup holders and for those who don't want Tartan Red or BRG there are 7 fetching shades of silver. What oil? Rich :-) |
| Rich |
| Rich Russians get everywhere! M1 0W40 Why see below Paul SAE Congress - Review by AE Haas Articles from the SAE conferences on powertrain and fluid systems in Tampa, Fl of October 2004 and the Paris 2000 conference. Here are some excepts: A New Method of Measuring Aeration and Deaeration of Fluids, Morgan et al: Air in oil causes oxidation, wasted power, higher oil temperatures, loss of lubricity among other adverse effects. Higher RPM increases aeration, so does increasing oil viscosity. Effect of Break-In and Operating Conditions on Piston Ring and Cylinder Bore Wear in SI (Spark-Ignition) Engines, Schneider et al: The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. The initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up. The SMAC, Under Pressure Oil Aeration Measurement System in Running Engines, Bregent et al: Oil aging, valve train and bearing problems and thermal problems occur with aeration. Below 110 C there is no problem but as one goes up the aeration ratio increases rapidly. (A cooler running engine from a thinner, faster flowing oil may lubricate better for this reason alone - aeration was a “hot” topic). Development of the Sequence IV A Valve Train Wear Lubrication Test:Part 1, Sagawa et al: Viscosity data reveals that the more viscous oil did not significantly alter the cam angle of minimum oil film thickness. Of greater importance is the finding that the higher viscosity oil continued to exhibit boundary layer lubrication. (Ergo thicker is not necessarily better). The effect of engine intake air humidity was significant so that tests are now done with specified humidity conditions. It was postulated that fuel dilution of oil would elevate cam wear. Fuel dilution of 4.5 percent did not effect wear. (This would have the effect of lowering the viscosity about 1 grade). The Effects of Crankcase Oil Viscosity on Engine Friction at Low Temperatures, Cockbill et al: By using lower viscosity oils there is less friction, improved cold weather starting, improved fuel economy, a savings of starting system components and less wear by increasing the rate of oil pressurization and flow in the upper oil galleries. Development of the Sequence III G Engine Oil Certification Test, Clark et al: Engine tests were made more severe again. (Over the years the oil ratings have improved but this has always been despite the increase in testing severity. It was III ...D, E, F, and is now III G). The oil inlet temperature was decreased from 155 to 150 C. The test was 80 and is now 100 hours. There were 8 oil level adjustments allowed now there are 5. The inlet engine air temperature was raised from 27 to 35 C. The engine load was increased 25 percent. Despite all this the current 0W-20 oils were still GF-4 compliant and showed minimal wear characteristics as long as ZDP levels were higher than 0.03 percent. (The SM rated oils have levels of 0.08). Other papers showed how they always consider older engines when formulating new oils for full backwards compatibility. You should use the latest, highest rated oil in your car by definition all oils are backward compatible. Always use the oil with a lowest first number in the grade and for many reasons use synthetic but mainly because of less wear and tear at start-up! Low Temperature Oil Pumpability in Emission Controlled Diesel Engines, Mc Geehan et al: At 4 F it took 100 seconds to get up to pressure at the camshaft using a 15W-40 oil, 60 seconds for a 10W-30 oil and 40 seconds for a 5W-40 synthetic oil. The others was mineral oils, all were SJ rated. The final pressure was 10 PSI higher for the synthetic, “thinner” oil. The sequence was 500 RPM x 5 sec., then start, then idle at 1,200 RPM. The 15W-40 oil had zero pressure at the camshaft for 90 sec. The oil only took 8 sec. to get pressure into the main oil gallery. (? 1 - 2 sec to show pressure at the oil filter where the sender is usually located). The oil flow deficiency is from oil vortex formation in the pump and gelation. (If we extrapolate that the oil is half as thick at 40 F then according to some people you should get 1/2 the time lapses as recorded in this study. Also, if the oil is moving this slow (impossible according to the constant volume pump theory) then it would continue to flow this slow and only gradually increase flow as the engine oil temperature increases with operation. Even though the pressure is there we can see the flow must be slow. No flow, no lube.) Similar data was found in: The effects of Crankcase Oil Viscosity on Engine Friction at Low Temperatures, Cockbill et al. Fuel Efficient Lubricant Formulations for Passenger Cars or HD Trucks, Benard et al: Friction using a 50 wt oil decreased with less engine speed. Boundary lubrication is negligible. This is confirmed by the lack of effectiveness of friction modifiers. With a 20 wt oil friction decreases with increasing speed. Friction modifiers have an important role. Hydrodynamic lubrication increases with increasing engine speed. In an additive test, friction was tested using a 10W-30 mineral base oil without friction modifiers. 1 percent molybdenum dithiocarbamate increased friction 0.5 percent in one oil and decreased friction 5 percent in another oil. This is secondary to interaction with other additives in the base oil. When using 0.05 percent molybdenum dithiophosphate the friction decreased 8 percent. There was a 9 percent friction reduction adding 1 percent fatty acid C18 ester. (We see the effects of friction modifiers. It is clear you cannot just mix them together. One must look at the whole package to gain benefit with modifiers. Thicker oils gain little with the addition of friction modifiers. Are thick oils with a lot of modifiers just for marketing?) Engine Oil Pumpability Study in a HD Diesel Truck Engine, Neveu et al: This basically was a similar test at 5 F to the first test paper, similar results. Additional information was taken. They showed that the oil filter was bypassed with all oils for up to 150 seconds with the thickest 15W-40 oil. This was because of the relief valve opening from excessive oil pressures through the filter, as if the filter was clogged with particulates. (The dirty oil on the bottom of the sump gets picked up first and run through the engine without filtration. They recommended a better SAE test correlation for oils reaching wear prone areas as the upper engine in cool, rather then cold testing. More testing at realistic cool start-up weather needs to be studied. |
| Paul |
| Rich Sorry, out all day helping to lift an engine in and out of a B for a clutch change. Right, straight answer - they aren't making the B - it's called progress, but let's assume that in some timewarp we have the following scenario: Modern oils, modern machining, and engine management on a B - then the answer is a semi 10W40, or synth 0W40. We have a mix of sliding contact (hydrodynamic) rolling contact (elastohydrodynamic) and boundary lubrication. Therefore we need a good AW package, with friction modifiers (or natural AW properties) for the low temp start-up. We also need a good film strength, and we need shear stabilty. All of these are provided in the Synth basestocks. We also need a reasonable viscosity to protect the bearings, but with good film/shear strength, viscosity can be reduced from what we previously saw as the norm. HTH Martin |
| Martin ZT |
| Thanks Martin, cold in my garage, hope your day was good! You and Paul both changed the engine spec and really cannot see the poor old thing as it is :-) I must confess that after posting the question I found it hard to think of a modern day equivalent to the B engine, since they stopped making the Lada. But, accepting that, I don't think you'd make an oil sale for an 1800, 95 bhp, cast iron, pushrod, carburettor engine with anything better than current mineral. We could compromise I guess, how about selling them semi-synth as a Special Tuning upgrade? Rich |
| Rich |
| Rich If Mineral and Synthetic were same price in your favourite grade, which would you choose? Paul |
| Paul |
| That's easy, if they were also the same grade I'd use either, and would certainly give synthetic a go as I know it works in other engines. Which synthetic would you suggest I could try in a fairly standard B at the moment? I've not seen a 20W/50 but is there a 10W or 15W/50 which might be OK? I really wouldn't use a 0W or 5W, so don't say M1, but is there anything heavier? I've used Mobil 1 in our lawnmower from new 19 years ago as there weren't many choices which met the spec and it only takes a litre on a change. It's air cooled, runs hot but needs something thin as its mostly splash lube. It gets a change every other season and the B&S manual suggests synthetic. Also used it in 2 Saab turbo daily drivers as it met the spec. Not sure about the type in our VW diesel. It's Pump Duesse engine and VW still have a monopoly on the oil they say can be used so we go with that and haven't had problems. Rich |
| Rich |
| Rich M1 15W50! http://www.redlineoil.com/products_motoroil.asp Redline have 20W60 they also have a 2wt Race This site has some details on a variety of oils and in UK the M1 choice is very limited http://www.opieoils.co.uk/lubricants.htm I checked Mobil site and for a 1980 B (was not expecting that)the recommendation was below 0c 5W20 and above 15W50 However if you change to a Synth then this may clean your engine, this should not happen if a mineral has kept your engine clean! may also identify any dodgy seals! M1 in Lawnmower but not B! Paul |
| Paul |
| M1 in lawnmower, recycled chip fat in B ;-) Well, interesting Mobil site, I went to their oil selector, http://www.mobiloil.com/USA-English/MotorOil/Car_Care/Vehicle_Chooser/VehicleChooser.aspx?option=2 and filled it out for a 11000 mile B and it definitely comes up with 15W/50. Then tried it for both lesser protection levels and it says, <<Our product lineup does not have a product at this protection level matching the viscosity recommended for your vehicle.>> which I take to mean 15W minimum as they have 10W in the range. Rich |
| Rich |
| I don't trust their web site to be anything other than a parroting of the manufacturers' reccomentations. Mobil up until very recently has been reccomending oil changes at manufacturer's intervals. They also repeat the manufacturers reccomendations for oil viscosity. They have been very conservative in their reccomendations in public. Apparently they don't want to be sued if the engine fails and an owner says it is because of the oil. In the last few months they have started advertising that their new oil can go for an extended period before changing. This representation is a first. Barry |
| Barry Parkinson |
| I suppose we can't blame them for that approach Barry. There are a lot of folk think they know better than the manufacturers, or simply stick anything in the engine carried away with boy racer thoughts. Ironic their adverts maybe cause that sort of thinking. Synthetic may be good but it's not magic and if the grade's wrong, it's wrong. Interesting they approve 15W so they may have thought that out for themselves, or did the later 1980 cars go to that? I think Duckhams had Hypergrade 15W/50 out by then and the industry was moving towards lighter oils in new cars. Rich |
| Rich |
| Rich, I agree with Barry's comments and the Synthetic Oil Life Study has shown that these oils can go 18k This link should give 5W20 recommendation http://www.mobiloil.com/usa-english/motoroil/car_care/which_oil/WhichOilOption2.aspx Paul |
| Paul |
| Copy and paste Current Vehicle: Year: 1980 Make: MG Model: MGB Engine Type: 4 cyl. 1.8 Liter Ultimate Protection Mobil 1 5W-20 A fully synthetic motor oil, Mobil 1 5W-20 with SuperSyn Technology exceeds the industry's toughest standards and outperforms all conventional oils. Mobil 1 is recommended by leading car manufacturers as initial fill. |
| Paul |
| Nope, your link gives the same result as mine, <<Mobil 1 Extended Performance 15W-50 Mobil 1 Extended Performance 15W-50 fully synthetic motor oil is designed for today's longer service intervals. It provides guaranteed performance and protection for 15,000 miles or one year. Mobil 1 Extended Performance products contain 50 percent more SuperSyn, 37 percent more cleaning agents, and 36 percent more anti-wear additives than Mobil 1. >> So no problem there with the extended change interval and they call it guaranteed performance. But they only recommend that grade for a B unless I'm not doing it right, I cleared temp files. Anyone else checked through for a B? Rich |
| Rich |
| OK, got it I think, Paul, you must have entered "Below 0°F" to get that result. |
| Rich |
| Rich Living in UK it does occasionally happen. One Size fits all http://www.mobil.com/Australia-English/Lubes/PDS/GLXXENPVLMOMobil1_5W-50.asp Maybe of interest to you http://www.lincolnsonline.com/article105.html Paul |
| Paul |
| The additional additives for long life, fit with a long term mobil 1 oil test that was and may still be on the web. An older Camaro V8 was run with synthetic for more than 20,000 miles. It used a little oil and had a quart added about every 6000 miles with the oil filter change, as I recall. The periodic lab tests confirmed that the oil was still good, but the additive package was depleted in that mileage. With the addition of one quart of oil, the oil was back to standard. The conclusion was that long interval changes were fine with the addition of a quart every so often. A strategy might be to use regular syn oil and add a quart of the new stuff after several thousand miles to replace the necessary additives. One of the advantages to having a car with poor oil control, is that you are frequently refreshing the additive package. Barry |
| Barry Parkinson |
This thread was discussed between 07/04/2005 and 12/04/2005
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