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What weight oil you use depends largely on oil temp and bearing clearance.
A 2owt would work fine up to about 180
30wt up to 200
50wt over 200
A 50wt at 215 degrees has the same viscosity as a 30wt at 180 degrees.
I run my car on the street and see 220+ oil temps all the time. If I ran a 5w20 I would have no oil psi.
A drag car that never gets above 160 could use a 5w20 no problem.

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