Porsche Enthusiasts Club Forum

Bob,
No friction from my point of view - I quite enjoy a good erudite debate. Particularly, when I feel I might be able to contribute in some small way.

I think it's fairly safe to assume that you are correct about the engines past service history if it is the original 180k mile engine fitted at the factory. Certainly, in the case of that particular car with the information you have to hand I think your choice of oil in conjunction with adhering to the 'old school' practice of frequent changes is absolutely the way to go. Even at 180k miles, assuming everything is still within tolerances, with a proper maintenance schedule, there's every reason to expect to achieve another 100k miles from the engine.

To touch on some of the points you raised:
Yes, if any sludge dislodged by detergents manages to find it's way to the oil filter then that is of course a great result. However, before the sludge reaches the oil filter it has to run the gauntlet of passing through the fine oil galleries in the top end of the engine which, being so small, are prone to getting blocked up. This will result in oil starvation to the top end and therefore mechanical failure. This is why the best thing to do for an older engine is to leave the sludge where it is - a case of don't fix what isn't broken, if you will! You are correct, however, in that semi synthetics tend not to have additive packages with much in the way of detergent properties and I’m 100% behind you in that the service interval need not be extended beyond perhaps an extra 500 since carbon deposits are still going to build up anyway.

Bob you intimated that "surely semi synthetic oils must be better than a straight mineral oil". However, it’s not as black and white as that. The answer is, once again, it depends on the application. In the instance of your car, then absolutely the semi synth will offer you the best protection vs cost.
However, in the case of a new build flat tappet engine there has been a great deal of problems of late where by freshly built engines have destroyed themselves through no fault of the manufacture. In the not too distant past there was a tightening up of the rules as to what the oil companies can and cannot use in their additive packages. The result was that certain oils, which have been sold for years have, had to have their formulas changed quite dramatically. Without drawing this post out too much farther off topic than it already is, the key issue is the molybdenum content of blends X, Y and Z are now much lower than they have been when first introduced. The nock on effect being that blend X Y and Z is simply unable to do it’s job. On a flat tappet engine this simply manifests itself as camshaft failure. In this instance, the old fashioned mineral blends clearly offer the best protection in this type of engine.
Then the next point is there’s mineral oil and there’s mineral oil – take for example the cheap as chips 20w50 grade that you may well find on the shelf at your local supermarket at around £5 for 5 litres. The oil companies have to make a profit, the supermarket has to make a profit, then there’s the cost of processing the oil (more about that in a second) and also the cost of transporting and packaging it. Now, at a fiver a bottle, something has to be missing from somewhere. As with everything else made to a budget – the quality suffers. What you are actually getting for your £5 bottle of oil is recycled oil from your local dump which has been filtered and refined. You can pour it in your engine but it’s only going to do it’s job for about 1000 miles if that. Not good.

On a lighter note – I am an MG man at heart and I too share your penchant for Duckhams 20w50. The nice thing about that is it’s green - stick with me on this one… On an MGB (which is my usual car of choice I have to admit) it’s best to use 20w50 in the gearbox as well as the engine. After a couple of cycles around an engine the oil blackens with carbon deposits. So, when the car marks it’s territory all over the drive, depending on the colour I know whether to attack the engine or the transmission for leaks. It’s nice when a car tells you what needs fixing without having to fault-find, eh?!!

I keep seeing the moniker “oilman” mentioned – are you the same oilman from Britcars? If so, hi! I post on there as JC.

Cheers,

Jon.

Many thanks for your help, you guys.
Thanks especially to you Jon for a most illuminating discourse/discussion into the differences in oils.
All servicing gear now with me - let me get my hands mucky and let servicing commence!!!

Again, thanks.
Bob

K&N filter £11 posted on ebay, don't need the tool if you have a 27mm socket

Well I've run mine for a month on 10/40 semi now and all is well, I did add a flush and ran it for 50 odd mls before the change, new oil in its still as clear as the day it went in, no leaks and the engine is running fine on it.

quick 2 penne'th I have always found a call to Guy at Opie oils will be as good advice as you can get, but I have to say that what Jim has said with his many years experience of these old cars, you will not go far wrong

Just saw 4lt 10w40 Castrol GTX in Asda for £10. Seems very cheap for anyone planning on doing their oil.

Got to say I changed the oil myself on my old Golf and probably won't do it again. Although it's an easy job it's a bit messy and you have to get rid of all the oil afterwards.

Back to the Drain Plug ring....900 123 118 30 22X27 all models!

Cheers, 951jamie,
Slack handfull ordered from Europarts (now 42p)