Engine oil explained

[audihere06]

For those interested oil nerds, or anyone who wants to know the excruciating details of all there is to know about engine oils. I found this article by Dr. Ali E. Haas while researching the best oil for my next oil change. It is very well written and easy enough to understand. Enjoy....

http://ferrarichat.com/forum/faq.php?faq=haas_articles


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[Schweini]

Cool, ill give that a read when Im off work

Heres another fantastic analysis I quite like. Great read as well:

http://www.bobistheoilguy.com/

[UberTeile]

The paths of Dr. Haas & BITOG have crossed in the past....both are excellent sources of info. IIRC, Dr. Haas is in the "thinner viscosity is better" camp....and in many ways he is correct.

[MrBigglesworth]

Great links - thanks - only part way through the education though!

One thing I do find interesting is that here in the EU something like castrol edge 5W30 is recommended to meet VW504 spec for the 2.0T - but reading the first article above (so far) 0W30 would be better. But Castrol Edge 0W30 is only VW502 rated. Is the difference between VW502 and VW504 just that 504 is long life spec? If you were going to change your oil <10k miles and <1 year, then could you drop to VW502 spec with no real risk?

[audihere06]

Great links - thanks - only part way through the education though!

One thing I do find interesting is that here in the EU something like castrol edge 5W30 is recommended to meet VW504 spec for the 2.0T - but reading the first article above (so far) 0W30 would be better. But Castrol Edge 0W30 is only VW502 rated. Is the difference between VW502 and VW504 just that 504 is long life spec? If you were going to change your oil <10k miles and <1 year, then could you drop to VW502 spec with no real risk?

Between the two and especially here in the US, I would go with the castrol syntec 0w30 because it is the only one that is a group 4 PAO based synthetic. That alone will extend the life of the oil because it is a true synthetic. All the other castrol "synthetic" in the US is group 3 hydrocracked crude oil. I wouldn't get too hung up on vw spec oils. There are tons of better oils out there that are not vw specd because its so expensive to get specd by vw. Another way to see the real world life of each oil is to look around online for virgin oil analysis and used oil analysis and compare.


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[audihere06]

Great links - thanks - only part way through the education though!

One thing I do find interesting is that here in the EU

Oops didnt see that you are in Europe. In Europe you will have access to much better oil than we get here. So basically just make sure whatever you buy is a group 4 or 5 synthetic. A group 5 ester base will offer even more protection and last longer. Personally i will be running redline 0w40.



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[Brillo]

Dr. Haas is right about many things regarding lubrication but the devil is in the details. He never really addresses hydrodynamic lubrication theory and how moving surfaces with oil in-between still have a protective fluid film thickness separating the bearing surfaces, and that higher viscosity oils have a higher fluid film thickness. Clearly, this is an important consideration regarding cold engine starts. (But also a good reason not to beat your car until the engine warms up.) Read Duncan Dowson's work (Leeds University) if interested in the technical minutia. The other area that Dr. Haas doesn't properly consider is regarding the claim that in some conditions (racing for example) the oil temperature can reach 302 degrees F. While it may be true that in some areas of the engine the oil can momentarily reach that temperature, in the critical bearing areas it never reaches these high temperatures. This is an extremely important consideration! By design, these critical lubrication areas would be the bearing surfaces the oil is pumped to immediately out of the oil sump such as the main bearings and journals of the crankshaft. I seriously doubt that even the cam bearings also lubricated by oil directly from the sump reach much over 212, certainly not 302 degrees. The wrist pin-rod bearings probably are the hottest of the critical bearing surfaces but again, likely nowhere near 302 degrees given the quantity of oil being pumped through these bearings combined with the fact that the aluminum piston is very effective at drawing heat away. Certainly the head temperatures are hotter than the block but nowhere near 302 degrees or we'd be blowing a lot of radiators. I drive a water-cooled Harley motorcycle with an accurate (calibrated) sump oil temp gauge and even on the hottest days of the year (95 degrees ambient) the oil never goes above 210 degrees even when driving quite aggressively. That's my 2 cents worth for you to consider. Comments are welcome. Brillo

[Brillo]

The point I wanted to make is that I don't find Dr. Haas' commentary regarding viscosity and oil temps at 302 degrees to be particularly relevant. The other this I forgot to mention above is in regard to those of us running 2.0L turbocharged engines. I know the turbo bearing is oil lubricated but have no idea how hot the oil gets in that bearing. Fortunately, while temperatures may be high, the stresses there are quite low. This is the one area where I would be most concerned about cooking the oil, especially when driving in a 'spirited' manner. Brillo

[audihere06]

The other this I forgot to mention above is in regard to those of us running 2.0L turbocharged engines. I know the turbo bearing is oil lubricated but have no idea how hot the oil gets in that bearing. Brillo

This is why I am still sticking to a 0w40 instead of immediately running out for the thinnest oil i can find. Perhaps this is also the reason Borg Warner changed the bearing for the K03. I suppose they found flow to be more beneficial to the turbo than pressure. There has to be a happy medium between pressure and flow. The oil I have chosen (redline 0w40) has a higher HTHS rating than many competitors especially castrol. It also contains quite a bit of moly and is ester based. Thank you for contributing to the thread. I am hoping many more people will share their knowledge.



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