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Originally Posted by ruturaj001
Thanks everyone. I understand high temperatures mean lower viscosity which results in lower pressure.
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"lower" pressure isn't necessarily a problem, you only need pressure sufficient to keep the bearings fed. In the "working zone", hydrodynamic wedge is what supports the crank in the main bearings and the rods in the crank. HTHS is probably a better number to look at for oils to see how well they do there. Fixation on oil pressure and thinking "more is always better" is IMO somewhat misguided.
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Oil cooler also reduces pressure at all temperature ranges. At 260°F the oil viscosity is 7.8 and 8.4 approximately for Pennzoil euro L 5w30 and Mobil1 FS 0w40, assuming oil cooler kept temperature at 212°F the viscosity would have been be 12.5 ans 13.8 instead. My question would be which is lower
Oil pressure at 260 without external oil cooler
Oil pressure at 212 with external oil cooler
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You might need an oil cooler as big as your radiator to keep oil temps to 212F. Most seem to knock max temps down from ~275F to ~250F under track usage.
Attaching pic of graph showing the *same* oil pressure running 5w30 without an oil cooler at ~275F and with an oil cooler at ~250F, from this thread:
https://www.ft86club.com/forums/showthread.php?t=91820
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I understand at say 300°F as highest temperature without oil cooler, it would be better to have oil cooler and lower temperature. And at low temperature it would be worse to have oil cooler, pressure wise. What's the tipping point? 260°F? If so why?
Sorry about lots of questions, just trying to understand and thanks everyone for reply.
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In my experience so far, these cars, last-gen and current-gen, are fine without running an oil cooler for track usage. Oil temp for me always climbs to 270-275F over a handful of laps and stabilizes.
If you're strictly worried about pressure, run 40-weight synthetic, it will give you higher pressure at 275F than 0w20 at probably 230F.
Me, I usually run 5w30 Redline (HTHS 3.7) at the track, though I have also done track events with Subaru 0w20....