Quote:
Originally Posted by Dzmitry
Haha, I understand your analysis of all this. And I am not going to dig too far as this has been a conversation in multiple threads I have had with others about oil pressures, temperatures, ideals, etc etc... But the reason I say what I say, is based on data that people have compiled for this platform over all these years. To specifically point out a question you ask, 15w-50 is too thick just because of the oil pressures the car sees at low temperatures and reasonable high temperatures within 230-240F. They can often be too high than what the spec calls for on this car. 5w-30 on the other hand see's a fairly minimal pressure change at low temperatures, and extremely small pressure changes at high temperatures. There is data for all of this flowing around these forums, so please don't ask me to quote it as I am just being general and not trying to start a full topic.
It is not as simple as "5w-30 is better because it's thicker". It all depends on your application and driving style and whether the car is tracked and how much, etc. 5w-30 can be acceptable because of oil thickness properties at that rating are similar to that of 0w-20, and not far off. 15w-50 on the other hand has significantly different thickness properties throughout all the temperatures ranges our platform experiences. A simple search of the two different types of oils will give you their viscosities, and you could graph it out to see how they vary.
In general, you are correct, there is no need for thicker oils for a DD. I was simply throwing the option of a slightly higher weight due to the fact that I don't know OP's driving style or oil temps that he see's. He also mentioned going forced induction in the near future, which will certainly be raising his oil temps.
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I believe the point at which 5w-30 would exceed 0w-20 in overall "protection" is probably around 220-230F. vast majority of people are not seeing 230F on a DD. and I would first recommend trying to get oil temps under control via oil cooler and/or hood vents before making the switch, or maybe using 5w-30 during track season (assuming you are tracking) and 0W-20 for non track season.
For a pure DD the time spent below 180F for many people is probably much longer than the time spent above 200F and especially 220F+. I would rather have 0w-20 with sub 180F oil. It is probably a wash between 180-220F, and 5W-30 starts to become more advantageous 220F+
FI can raise temps sure, but should always be accompanied by an oil cooler in my opinion which would negate that for a DD.
I think we are in an agreeance that in more extreme cases like tracking 5w-30 might not be a bad idea.
but the vast majority of owners do not track and the vast majority of DDers are not pushing the car hard enough on the streets to warrant the switch to heavier weight oil in my opinion, especially if they have an oil cooler. I think at best the 5w-30 is no better or worse than 0W-20 in this case, and at worst it is actually doing more harm than good because of the added cold start / low temp wear. which goes back to my last post, only implement an "optional" recommendation if it will undoubtedly enhance or strengthen your application.