Quote:
Originally Posted by ZDan
You'd run thicker oil at the track not to preserve its viscosity after it cools back down from elevated temps, but to have the appropriate viscosity at elevated temperatures. I.e., if your oil runs up to, say, 275F at the track, a 30, 40 or 50 weight oil is going to be a lot closer to the right viscosity than a 0W20, which might be dangerously thin at that temperature.
(Obviously you'll want synthetic if you are running elevated oil temperatures, whatever weight you run.)
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Right, I'm just speculating that at say 275F, a 50 weight still might not be "within spec". I haven't looked up any data but on BITOG there's a chart saying that 30 weight oil is about 3cSt at 300F, which is much thinner than the 7-8 cSt of 20 weight oil at 212F.
And even with synthetic you would want to be careful about oil temps since the oil does cool the piston and stuff like that which are much hotter than the average oil temp and can oxidize the oil quickly.