Anyone running 10W50 or 20W50?

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04-19-2011, 03:54 PM

JasonC SBB

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Anyone running 10W50 or 20W50?

So i have lowish warm oil pressured due to running a non-VVT (thin) oil pump with a VVT head.

I'm talking 40 psi warm max.

So, I'm thinking of switching to xW50 oil, to improve the film strength.

Any downsides to this?

04-19-2011, 04:18 PM

Laur3ns

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Castrol 10W60 here in all race cars. Good stuff.

04-19-2011, 04:36 PM

Import Al

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My last oil change was 20w-50 synthetic (Valvoline), band-aid for a FUBAR'd exhaust valve. The rebuilt head arrives today, but it ran quiet & cooler with 20w50 vs Rotella T6 5w-40. Fuel mileage dropped 1-2 mpg vs the 5w-40.

I'll try to find the thread about issues with too viscous oils from BITOG, potential friction increase IIRC. Miata tolerances (PTW, bearings etc.) are typically tighter then motorcycles & rotaries, OEM 20w50 users. I'm assuming the thicker oil's minimum film thickness & slower flow might not create as constant a film?