Quote:
Originally Posted by Element Tuning
Now I'm recommending people put 40w race oil in their street car but its not a bad idea to step it up a little on N.A. and with boosted don't be afraid to put in 10-30 or 10-40 as your engine bearings will thank you in the long run.
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This is interesting because I experienced the opposite. I started with 5w-30 (a heavy one) and switched to real 0w20 Mazda (high moly GL5). My thought is the screens and passages in the heads are sized for thin oil. We've already seen that the true 0w20 keeps the engine cooler (more flow.)
You are probably right about the crank and rod bearings but those are cut differently than the Ej's also.
The vvt had to be designed around a certain viscosity range as its all hydraulic with the oil being the fluid.
I think many with the complaints are using redline 0w-20 which is really a 30 weight.
I've got an open mind and not saying you are wrong but I swear my engine is quieter and smoother at low revs with real 0w20.
An oil pressure gauge would settle the question? May be more of an oil pump issue than anything.