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Originally Posted by dowroa
@ Frost, then are you matching the viscosity charts of your oil at 270 to the spec that Subaru has for the tolerances of the FA24 (and I am not sure if RPM is dictated in this spec)? |
Engines designed to run over a *very* wide range of operating temps can handle a *very* wide range of oil viscosity.
Pretty likely that Subaru and/or Toyota have repeatedly tested this engine to redline (oil temp goes up with revs) with factory fill 0w20.
Still, for repeated track usage, with oil temps at 270-275F, IMO it's a good idea to run 30 weight at least. The manual even mentions running higher viscosity for sustained high temperature environment and/or usage.
Again, viscosity of 5w30 at 275F is about the same as 0w20 at 250F.
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I know this is a topic older than time, and I am more than happy to look into this more but I am not aware if general users are given the specifics to make a claim that 270*F is OK with Oil-X at weight Aw-B to maintain an appropriate film with C-hours and a max of D thermal cycles of the oil.
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As far as that goes, neither does anyone have specifics to make that claim at 250*F either...
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When in doubt, why not run cooler and conservative? Then the problem is no longer a min/max or limits issue?
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Throwing additional parts + oil lines + connections = points of failure at a problem that doesn't really exist, may not *really* be the "conservative" approach...
For track-dedicated cars that see much longer stints (full races or endurance), yeah, you might want to run a cooler, if just for some additional margin so you can tolerate more and not have to back off in a race, particularly if being in traffic affects cooling airflow.
My car is my daily-driver and sees usage in sub-freezing winter months. Even with a thermostat, these cars with aftermarket added-on oil coolers likely won't get oil up to temp ever for those months. Not good...
And for me, on track I'm never in a lot of traffic (if I find myself in a "train" it's no biggie to just pull in and drive down pit road), my oil temp never tries to "run away" on me during the stints I run.
For *me*, the more conservative approach is to just run 5w30 at ~272F and not worry about running an oil cooler.