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MG MGA - Engine Oil Change Time

There was something in one of the threads a month or two ago about an additive that had been removed from many petrol engine oils and this was causing great concern to members with newly built engines. If I remember correctly the recommendation was to switch to diesel engine oil for running in.

I am just about to do a routine oil change on my 12,000 mile engine and would welcome comments.

I have been using Miller's Semi-Synthetic Classic 20-50 quite happily for the past few years. However, I am aware from previous threads that many users, across the pond in particular, use fully synthetic oils, usually in the region of 5-40 or 10-40. I was in my local shop at lunchtime and spotted Miller's Fully Synthetic 10-40 for diesel and petrol engines. Could this be something to consider? What would I need to look out for in the contents list on the can?

Steve
Steve Gyles

Steve,
the problem with US oils is that the ZDDP (zinc dialkyl dithiophosphate) was taken out This was removed because the phosphorous in the compound damages catalytic converters, so I imagine that the same thing has happened on your side of the pond, too. As I remember, diesel 30 wt maintained the zddp, although it may be leaving too.
Basically, the lack of a good high pressure anti-wear additive will cause your cam lobes to be cam circles. I also understand that after the engine is broken in, with good camlube during the break in, that it may be unnecessary.
You may wish to check out the archives.
Mike
Mike Parker

In general US SM oils have reduced ZDDP. UK oils are SL and have higher ZDDP.

Paul Wiley

Steve

This is the long amswer

An engine oil that contains about 0.1% phosphorus or higher, will easily provide the required anti wear properties for older engines.

The step from API SH to API SL was accomplished by a combination of new additives or adding additional anti wear and anti oxidant to existing blends. These were not phosphorus based, but used organic molybdenum additives (not molybdenum disulphide - aftermarket oil additive), to keep phosphorus levels at 0.1%.

Now we have API SM – for the first time, the limit on phosphorus is from 0.06-0.08%. There are industry concerns about the applicability of these oils in older engines. However, the limit only applies to 0W-20, 0W-30, 5W-20, 5W-30 and 10W-30 oils (so called “ILSAC” grades). Any other grades are exempt from this.

Therefore even blanket statements about API SM oils will be incorrect and further research will be needed by the end user.


There is one other factor with non-ILSAC oil grades. If they also have the European ACEA A2/A3 with B2/B3 or B4 performance levels, phosphorus levels will also be at 0.10 % to 0.12% as their tests have been more severe than the API for some time. Hence an oil that is SL (SM)/CF/A3/B3 also well exceeds the anti-wear requirements for older engines.

The irony is that API SF and SG oils formulated in recent years usually have phosphorus contents of around 0.08% (usually 0.1% maximum) anyway due to other advances in technology, unless the blender chooses to add extra additive.
Paul Wiley

OK

I now have in front of me the notes I took in my local motor factor. It's a Millers Oils petrol & diesel engine oil. Labelled XSS, it is a 10W-40 Hi-Synthetic formulation. The small print says "Exceeds latest ACEA A3 B3 specifications."

Yes or no for my 15,000 mile (not 12,000 as previously stated) 1800 engine?

Steve
Steve Gyles

Steve

For normal road use should do very well.
http://www.millersoils.net/index2.html

Paul Wiley

Thanks Paul and for the link.

Steve
Steve Gyles

I changed my oil today and I had decided to replace the filter with a spin on adapter

If you think changing an old style filter is awkward try fitting a spin on adapter. The instructions glibly say - after removing old filter , remove splash plate. This is a disc in the fitting on the block. It is free to rotate but appeared to be held in by a circlip of some sort. After much scraping of knuckles trying to release the clip I was dispairing. It is so difficult to get at. I finally resorted to trying to prise the disc out and - ping - out it popped. No sign of a clip. It just seems to be retained by a lip on the oil feed tube. Fitting the adapter is then straight forward and the job was soon done.
To get back to the thread topic I use Halfords 10w 40 semi synthetic which is excellent value and I've been using it for years. Oil consumption is negligible and I change it every couple of years. Paul - I have no idea whether it contains phosphorus. My last encounter with phosphorus was in the chemistry lab at school some time in the swinging sixties. It has a wonderful property of self igniting.
David
David Marklew

David

Halfords oils which I should be from Esso will contain ZDDP and should be SL A3 B3

Ehe workins of ZDDP


http://www.apmaths.uwo.ca/~mmuser/Papers/TL05.pdf
Paul Wiley

Dave

A number of us use the spin on adapter. The gotcha can be to fail to remove the old, sometimes solidified, sealing ring and then place the new one, that comes with the kit, on top. The result is interesting oil leaks when the engine gets thoroughly warmed up. I lost my entire oil contents in a matter of minutes on the M6 to such a leak about 8 years ago.

Steve
Steve Gyles

I have just changed my oil from my normal 20-50 semi synthetic to the 10-40 semi synthetic I referred to above. First thing I have noticed is that I seem to have a higher oil pressure - 70 psi at cold instead of about 63psi before (1800 engine). would this be correct?

Steve
Steve Gyles

I was convinced by this thread,

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=archiveth&archiveyear=8_2007.dat&access=&subject=8&subjectar=8&source=T&thread=200610090226352026

and a new engine done-in by a lubrication failure and flattened cam lobs, that a change from my standard Castrol GTX to a higher ZDDP oil was needed.

I landed on Valvoline Racing VR1:

http://www.valvoline.com/pages/products/product_detail.asp?product=50
Steve Meline

Steve Gyles, - Yes, low oil pressure immediately after cold start up is a problem with 20W50 oil, from about 45dF or lower. The stuff just does not flow well when cold. With 32dF (0dC) or colder startup you might see a maximum of 20 PSI (or lower). It may take several minutes of running time to warm up enough to show normal high running pressure on the gauge.

The solution is to switch to 10W40 oil for cold weather running. This also makes it easier to crank start from cold. If you drive regularly in temperatures below 10dF you might consider using 10W30 oil (caveots to the lack of ZDDP addatives).
Barney Gaylord

Thanks Barney.
Steve Gyles

More importantly Steve the cold pressure readings are compounded by the measuring tube to the gauge. A heavy oil in cold weather causes a large pressure drop in the tube from the engine to the gauge and the reading at the gauge may well be far lower than the real reading.
Bob (robert) yes Y8 is toast again :)

Thanks Bob. Ok explain the 'Y8 is toast again' Anything to do with MG Flame Wars?

Steve
Steve Gyles

Hi Guys,

this sounds very interesting, so here's a slight spin-off question. What oild would be best for a "tweeked" engine, say a 1950 fast road? Would 10W40 suffice or would I be better with something more exotic?

Cheers,

Grant :-0
G Hudson

Following this winter's complete programme of replacement of every oil seal, grommet and gasket on the car, I have just filled my engine with a Valvoline oil that meets the SL A3 B3 spec Paul identifies. It was labelled for Turbo and Diesel use, and was actually the cheapest of the non-supermarket brands on the shelf. At $20 for 4.5 litres, I was quite happy, some of the others were $60 or even more for the same quantity.

I poured the BP stuff I had into the gearbox, and filled the axle up with gear oil too last night. Bled the brakes as well.

Hoping when I go look tonight that all the joints and seal surfaces are dry........

dominic clancy

Thick oil does not affect the gauge reading due to the small bore tube. The restriction is not so much in the small tube, as the gauge requires only a small amout of oil motion to operate.

There is a small bore restrictor orifice in the connector fitting on the frame between the flex hose and the metal pipe. That is intended to damp out vibration of the gauge needle due to high frequency pressure pulses from the oil pump. The small orifice is what makes the gauge slow to react with cold oil. Once the pressure is up on the gauge the oil stops moving in the small pipe, just holding the pressure, restriction is irrelevent, and the gauge shows the right pressure.

When the gauge is showing low pressure at cold start, it really is low pressure at the point where the signal pipe is connected to the engine. This is at the back end of the main oil galley which feeds the main bearings. There is some oil flowing, just going slow through the engine at that point. The engine will do okay, as long as you don't run it too hard until the oil warms up and shows normal high pressure.
Barney Gaylord

Grant


If using a mineral oil the type of polymer used to generate the ‘multigrade’ performance of an oil is also important. There are expensive ‘shear-stable’ types that resist thinning during use.
The way to really reduce wear is to maintain ‘hydrodynamic’ or thick-film lubrication at the tappet/cam contact. This depends on viscosity and rubbing velocity, and is highly desirable from a wear point of view because there in no metal/metal contact. In ‘boundary’ or thin-film lubrication there is contact, and this is where the surface-active anti-wear compounds such as ZDDP and molyDTCs do their stuff. A fairly high viscosity shear-stable multigrade is an advantage.

There is a test called the ‘High Temperature High Shear Viscosity’ (HTHS) which is run at 150C in a close-clearance taper bearing rig and gives a better guide for high performance use, however its not always easily obtainable apart from high spec race oils.
Paul Wiley

This thread was discussed between 04/04/2007 and 10/04/2007

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.