Recently, I thought there was a thread on Main bearings, but I can't find it. My buddy likes 20w-50. I keep saying it's too thick unless you're racing and pre-heat your sump. But he claim's 20w-50 provides a "buffer" on start-up. Doesn't seem right... after letting your motor sit at any length of time, I would think most of the oil (since it was hot when you stopped the motor and the viscosity is at it’s lowest point in respect to the base oil grade) would drain into the sump over a short period of time. So according to Bob’s “State of Lubrication”, you’re most likely in mixed film or boundary lubrication at start-up and you need oil flow as fast as possible. Also, he doesn’t think it matters since you get 100K out of a car no matter what oil you put in. Still doesn’t explain the 20w-50 in a fresh motor. Only reason I can think of to run 20w-50 is if your oil pressure is lower than 10 lbs/1K RPM or you’re racing.
20w-50 Buffer in Main Bearings
- Thread starter GTOinWP
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20w50 can be used on engines with worn main bearings, it helps keep oil pressures up. Keep in mind though, if your mains are that worn out, its close to rebuild/junkyard time.
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