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MG TD TF 1500 - Oil and Octane Ratings
| I recently acquired my father-in-law's 53 TD Mark II. I read in the "New Oil for Old Cars" thread, that many of you use 20W-50 in combination with Lucas Oil Stabilizer. I'm pretty sure the crankcase currently holds 10W-40. It's low and needs oil. Question #1: Is it safe to add 20W-50 to the existing 10W-40, or should I wait for the next oil change? I plan on adding a small amount of Lucas Oil Stabilizer as well. Question #2: I'm currently burning 87 octane fuel. Is there any danger/benefit to using 91 or 93? I'd like to try a higher octane to see if I get any better performance in the higher gears, and prevent backfiring. Thanks! |
| Greg Williams |
| Greg, First thing...these cars were made to burn leaded fuel! Are you using a lead additive to your fuel mix? Unless some mods have been done to your engine you could burn up your valves if you are not! 20W-50 oil (or as I prefer to call it) "engine slug" is recomended. Our little cars are fairly well known for thier oil leaks ...this slows the process! I have a case of the new castroil that seems to be working for others quite well on order. Get with some local MG owners (mostly nice folks) they can get you pointed in the right direction as to the little things you should know about maintaining your new love! If you don't have one....get a manual and follow the recomended fluids before you make a costly mistake! The wrong fluids in brakes/shocks/& such can end up being a real nightmare...stay the hell away from "jiffy-lube" and such places..these people know nothing about these cars most of the time. Welcome to the club! Regards & Cheers, David #A1 55 TF 1500 |
| David Sheward |
| Greg - Unless your engine has been stage tuned and has higher compression than normal, there is no benefit in running higher octane fuel. The cars were designed to run on what was known in England as pool petrol, in other words, something slightly more refined than kerosene. If I remember correctly, it was somewhere around 75 octane by todays measurements. David Sherwood is correct in saying that the engines were designed for leaded fuel and that running them on unleaded fuel will eventually cause valve resession into the head. However, that said, I have been running my TD for 20 years on unleaded fuel and have put on over 80,000 miles, most of that at 4200 RPM and my valves are still not in need of new valve seats (sorry, David). My philosophy on the unleaded problem is that once the valves need to be replaced, I will have the head modified to unleaded specs. Until then, I just drive and enjoy the car. Good luck - Dave PS. No harm in waiting for an oil change to start using the 20W-50 oil. The cars were originally run on straight 30W in the summers and 20W in the winters. |
| David DuBois |
| Hi Greg, if you have a backfiring problem you probably have a leak in the exhaust somewhere. This always causes backfiring as oxygen enters the exhaust on a trailing throttle and the ignites the mixture. Only takes a leaking flange gasket or similar. Cheers, Paul. |
| Paul van Gool |
| I'm not convinced that a well aged iron head is any more prone to valve recession than the supposedly hardened seats rebuilders install to prevent same and won't have any of the problems associated with hardened seats dropping out. Leaded or non-leaded has nothing to do with octane and an equivalent octane should have the same timing. As Paul says, check the exhaust for leaks. |
| George B. |
| Learn something new every day! "I have been running my TD for 20 years on unleaded fuel".....David D., so you DO NOT use a lead additive to todays petrols? Anybody else out there running this way? Am I the only one using these products? I guess I just assumed we were all adding lead to our mix ...honestly never had the nerve not to use it! David |
| David Sheward |
| David - No additives, I just fill up with standard unleaded at the pump and drive off. I am sure that there is some truth to the calims of accelerated valve/valve seat wear caused by unleaded gas, but my experiance would indicate that it is not accelerated to the point of having to really worry about it. The original instructions with the cars was a valve job at 25,000 and an engine rebuild at 50,000. With the way most people drive the cars today, that is a life time of driving. For those of us that drive the cars a lot (as in almost everyday). The interval is just shortened a small amount by using unleaded fuel. Cheers - Dave |
| David DuBois |
| Thank you, gentlemen, for your responses. My TD Mark II has also been running on unleaded for about 20 years, so I feel it is relatively safe. BTW, I started using 93 octane, and it feels/sounds like it is running smoother--no backfires, particular when wound up. My theory is that the fuel is burning "hotter", and therefore not as much is leaking past the carbs and into the exhaust system. The Mark II has dual fuel pumps, one for each carb, so they're never starved for gas. I've discovered its a bit tricky to get the mixture just right--not too rich but just lean enough for all gears. It's still a h*ll of lot a fun! Regarding the potential leak in the exhaust system though, I think it is still a likely probability, and will definitely check it out---thanks Paul! I've also added the high mileage Castrol GTX 20W-50 and bought a quart of the Lucas Oil Stabilizer (not easy to find around here) to supplement it as well. I look forward to better performance and will post any results here. Thanks! |
| Greg Williams |
| TF 1250. We changed over from leaded to unleaded fuel last year. We now run on 95 octane plus Castrol additive. This is the sodium/potassium phosphide type and also contains ferrocene as a flame improver that is said to raise the octane equivalent of the fuel. Whatever the claims, we find that starting is easier and running distinctly sweeter on this mixture than on the old leaded fuel. Also the plugs no longer foul after a lot of slow traffic running. I suspect the explanation has something to do with a hotter flame front, so more efficient combustion process. For oil we use castrol GTX 10W/50 and find this maintains a noticeably higher pressure especially when hot. In the 70s I used GTX on Morris Minors and got similar pressure improvements. |
| Paul Joachim |
| Hello, I'm the new owner of a '52 TD #19622. It's a terrific car, and my wife and I are having a great time with it. I've also been wondering about oil types and the leaded/unleaded question. Our car had an older restore, and the compression varies only slightly between 160-170. I've been running 92 octane-no additive, and the engine seems happy, but I want to do the right thing. A question: have any of you T-series owners ever seen a car with a metal painted rim casing on the spare tire holder? Our car has it, looks sharp, but I've not seen another vehicle with it. An aftermarket accessory - something carved out of a '56 T-Bird, what? Regards, Dan G> |
| Dan G> |
| My 2cents worth...don't know about long-term effects of burning unleaded, but here's what I recall about octane from an engine course in college many years ago. The octane rating is a measure of how fast the gas burns. The higher the rating, the slower it burns. A given quantity of gas has a certain amount of energy, regardless of its octane rating. The gas is supposed to burn at a certain rate in each cylinder, not explode. As the engine gets older, it looses compression and develops hot spots, causing the gas to burn quicker. You hear that as pinging or knocking, and probably feel a slight loss of power. The higher octane gas helps to slow the burning to the rate it should be in a properly-operating engine. General advice for any car is to use the octane rating recommended by the manufacturer (some new cars do require higher octane). If the engine knocks, try higher octane. If the engine operates properly, the higher octane gas will not improve power and have no effect, except to your wallet. |
| Steve Markman |
| Apparently running on unbleaded when the head has not been modified will only cause serious damage if there is sutained high speed running; but don't sue me if this is wrong. Some peopel use aditives but on both the TD & TF we had the heads converted. This needs to be done by a good shop wioth the right machinery. There is equipment which will do it and ensure that the right sized valve seats are fitted. There have been cases where seats have come loose. Some say there is a drop in output but by skimming the ehad and having the car tuned by a man who knos on a rolling road excellent results are produced. Our TF fitted with a semi race cam does hit 80/85 mph and accelerates well. Drivers of Mercedes 500 SELs do not l;ike being overetaken by a 50 year old British sports car which probably cost less than the weekly depreciation on these German monoliths. Oil - we use 20/50 and pay about $8/9 per gallon. |
| Bob Marshall |
| Well fellows I have a very early TD #0533 with a nonmodified head and a shorrock supercharger. I run regular gas without additives and have had no problems for the past 4 years, and over 5000 miles. I will rebuild head when necessary, but have no desire to do so unless the valves and seats truely need to be replaced. Cheers, Rob |
| Rob Silverman |
| Paul J. mentions a Castrol fuel additive that is a "sodium/potassium phosphide type and also contains ferrocene". Is this marketed as Castrol Valvemaster Plus? If so, it appears to be available only in the UK and Australia. Is anyone in the states using a similar fuel additive? I'm sensitive about adding anything to the fuel system ("if it ain't broke, don't fix it"), but I'm curious to know if anyone else is modifying thier fuel mixture with cleaners/boosters. Also, for what it's worth, now that I'm using heavier oil (20W-50) with about 20% Lucas Oil Stabilizer, my oil pressure is very good, up from about 40 lbs to about 50-60 lbs. Greg W. 53 TD Mark II |
| Greg Williams |
| It suddenly occurred to me that everybody is always going on about "unleaded fuel will wear the valve seats faster" for possibly no reason. I can understand that concern in a new car that you are going to drive for 100 thousand miles or more, but we are talking about old cars that get driven mostly on the weekends. I wouldn't worry about it unless you have a daily driver or if your valve seats are already bad. |
| Norman Fair |
| All, I have seen "Lucas Oil Stabilizer" mentioned in a positive manner several times on the BB in the last few months. Is this product avalible at the normal chain/discount auto parts houses or is it a special order type of product? Dave |
| David M. Kalp |
| David K. Lucas oil products are avaiable in Georgia. I found the nearest dealer by a key word search. Bill |
| Bill Steffen |
| P.S. See the last poting under Drip, Drip, Dribble. |
| Bill Steffen |
| If you had a significant increase in valve seat wear would it become evident when checking your rocker clearances? Tony Cove |
| Tony Cove |
| I found Lucas Oil Stabilizer at my local NAPA and O'Reilly automotive stores. These are chains like Autozone, which I imagine would carry it also. The Lucas website has a search utility that lists distributors in your area and/or zip code, but it doesn't appear to be complete or current. Check your local auto discount store. Greg Williams '53 TD MG Mark II |
| Greg Williams |
| Dave Kalp: I found the Lucas product at Pep Boys. Don't know if there are any of their stores in your area. So far the stuff seems to help. I used to get a puddle about the size of a silver dollar after a pretty good run. Now it's about the size of a dime. It's effectivity is probably only slightly better as any leakage is really determined by the fit of the real seal anyway. I bought it originally to add to the gearbox and there is an improvement in the ease of shifting as well as somewhat of a noise reduction too. Doesn't shift as smooth as a modern car but not sure it ever did even when new. Hope that helps... Jim TF7022 |
| Jim Rice |
| Bill, Jim and Greg, Thanks. I did a google search and found that the NAPA store 4 miles from my house sells Lucas Oil products. I picked up a quart on the way home last night (not cheap at 7.99 at QT). When I change the oil this week end I will replace a quart of 20W50 with the Lucas Oil Sabilizer and see what happens. My leak is about three to four inches in diameter, so if I can get it down to silver dollar size it will be well worth the $8 a quart. Thanks again, Dave |
| David Kalp |
| Concerning valve wear and unleaded fuel, I received some clarification recently and will pass it along for what it is worth. As some of you have mentioned, if your car does not knock (ping) which is caused by preignition, then higher octane fuel is a waste of money. The only possible benefit is the detergent package which is included with the gasoline. If you buy a major brand gasoline, the detergent package in the regular fuel is fine. Preignition is caused by either too high a compression ratio for the gasoline or hot spots caused by carbon deposits. Our compression ratios are not too high for 87 octane fuel. If you have carbon deposits, using higher octane may help but the eventual solution is decarbonation. High rates of valve wear with unleaded gasoline is caused by the modifications put into the valve mechanisms to overcome the deposits of leaded compounds caused by using leaded gasoline. These modifications consist of the valve seat and valve surface angles being machined to be slightly different, causing a grinding action which removes deposits. Also the valve is made to turn, again causing a grinding action to remove deposits. If leaded gasoline is used, the grinding is designed to be just enough to remove the deposits, keeping the valve surfaces clean but not grinding metal. When unleaded is used, there are no deposits, so the grinding will work on the metal surface. This only becomes significant when the car is driven very hard. The question is, do our T types have these mechanisms or not? At our MG club, the consensus was that they do not. That's why the maintenance called for fairly frequent removal of the head and reseating of valves, presumably to remove lead compound deposits. This results in a plus for us. There are no fixes in place for the lead deposits and if unleaded is used, then the 87 octane is fine and there will be no grinding and no deposits. This makes sense to me, and explains why Dave Dubois gets away with his practice of just fill up with unleaded and don't worry. I do the same. Ron |
| Ron Coates |
| I hesitated to get into the oil grade discussion, but decided to comment after all. Oil has three purposes-- cooling, removal of debris and separation of metal surfaces. The most wear occurs on startup because there is no film of oil between metal surfaces until oil flow is established and pressure is built up. Flow will be maximized the thinner the oil. Surfaces will be best separated by more viscous oil provided the flow is adequate. Cooling and removal of debris will be high with rapid oil flow. The choice of oil is therefore a big compromise. Thin oil (low viscosity) on startup is desireable, but enough viscosity is required to maintain a film between surfaces when hot. Enough flow is required for cooling and debris removal. The answer to all of this is the development of multi viscosity oils. 10W40 for example behaves like 10 weight oil when cold and 40 weight oil when hot. The MG culture has settled on 20W50 in the main for T types. I would have guessed that 10W40 would have been a better choice. There is no way that I know of to determine the best oil except experience with wear. After reading this bulletin board in the past, I have settled on 20W50 based on members' experience. I would guess that 10W30 or 10W40 would be fine also. The only caution I would add is that there is a lot of reliance on oil pressure on this bulletin board. Higher viscosity will increase observed oil pressure, but may inhibit flow to the places required to maintain adequate oil film. I don't know whether 20W50 is sufficiently high to do this, but I doubt it since experience has settled on this grade. Ron |
| Ron Coates |
| Guys, remember these old XPAG engines were designed in the 40"s and have wide bearing tolerences as compared to a modern engine. You need this 20/50 to fill up the spaces in the bearings.. If you look in a modern day car manual you will see that they only use 10W and 5W blends. Why? They need oil flow with tight tolerence bearings. I am using the new Castrol GTX for High Mileage Cars and have noticed a little less leakage in the seal area, in the valve guides as well as a reduction in fuming. I change oil every 2000 miles and feel that any stability additive would be a waste of money. Most premium oils have this build in to the formula. TF 1250 @ 36,000 miles. |
| colin stafford |
| Guys, remember these old XPAG engines were designed in the 40"s and have wide bearing tolerences as compared to a modern engine. You need this 20/50 to fill up the spaces in the bearings.. If you look in a modern day car manual you will see that they only use 10W and 5W blends. Why? They need oil flow with tight tolerence bearings. I am using the new Castrol GTX for High Mileage Cars and have noticed a little less leakage in the seal area, in the valve guides as well as a reduction in fuming. I change oil every 2000 miles and feel that any stability additive would be a waste of money. Most premium oils have this built in to the formula. TF 1250 @ 36,000 miles. |
| colin stafford |
| <<<snip>>> have wide bearing tolerences <<<snip>>> This can be compensated for when the crank is reground during a rebuild. A good crank grinder will grind the journals to minimum for longevity, or maximum for looseness in a racing engine. Main bearing clearance: MG XPAG: 0.0008 to 0.003 Nissan Z22: 0.0008 to 0.0022 Valve seat angle: MG XPAG: 30 degrees Nissan Z22: 45 degrees on the seat, 45.5 on the valve (No lead engine) |
| Blake J. |
This thread was discussed between 22/05/2002 and 07/06/2002
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