Quote:
Originally Posted by wstar
I'm sorry, but that's faulty logic. The flashpoint on my first change of Nissan Ester 5W30, when it came out of the engine, was testing at 390F. Are you saying that if my oil temps were peaking at 350 I'd have nothing to worry about?
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I don't think that's what is being implied. This is what I've gathered from all this discussion and looking into it myslef...
From sources I've read and people I've talked with (and there has been quite a variety at this point), the flashpoint of an oil is a measure of how readily the oil actually breaks down from heat...the higher the flashpoint the more heat the oil can take before it starts to breakdown (Synthetics have a higher and in some cases a much, much higher flashpoint than non-synthetics).
All oils break down and heat is a major factor in that but the higher the flashpoint, the longer the oil life and the higher the temperatures it can tollerate before it breaks down. Or another way you can look at is that flashpoint indicates how
long the oil can do the job of protecting the engine before it becomes unable to do so and the higher the heat; the more frequently you should change your oil.
However, it is also true that the viscosity of the oil changes (thins) as oil increases in temperature so, all other things being equal (and they rarely ever are); the higher your engine oil temperature is, the less "protection" the oiled engine parts have because the viscosity gives a thinner and thinner layer of protection as the heat increases. This would be different from how long the oil can do its job but rather how
well it can do its job at any given temperature.
What I've yet to see anybody translate is how much or how little all this actually affects the life of an engine. If the 3.7 engine oil consistently runs at 240 degrees; how much sooner, on average will the engine fail than if it was consistently running at 220 or 200 or 180?
I think we can all agree that, 180 or 200 is "better" for engine life than 240 but that doesn't tell us how much better...at the consistent 220 mark, will the engine die at 210,000 miles instead of 220,000 or will it die at 155,000 instead of 220,000?
The bearings may well break down and fail "sooner" with high temps than not but how soon and will anyone own their 370 long enough to even find out??? I don't know the answer; if anyone actually does they should speak up!!!