Hey, back to the old viscosity debate.
My $0.02
Some guys here agree with me but there are guys that feel strongly that even in ??sporting driving? conditions, the OEM 5-30 is best for modern ??small clearance? engines.
I have gotten great results using SAE 40 to 50 single and multi grades for 30 years (yikes) and recently switched to 0-40 Mobil-1. This seems to drive some guys nuts, and now with the advent of 5-20 OEM recommendations some consider SAE 40 or 50 molasses.
OK, I finally got around to verifying what I suggested on these boards.
Directly out of the respective Mitchell repair manuals:
Rod bearing ??oil clearance? specs:
All figures are in ten-thousanths inch and (mm)
1983 Mustang 5.0 liter 0.8 - 1.5 (.020 - .038)
(eng has same specs as the unit that I used to compete with in 1972 SCCA events w/ SAE 50 oil)
2000 Contour 1.1 ?? 2.5 (.028 - .064)
Decades apart yet very similar nominal rod bearing oil clearance specs. In fact according to Mitchell the newer car has more rod bearing clearance.
So much for that urban legand.
Last week I put a question to the Penzoil tech line: I have a late 90??s car out of warranty, I want the longest engine life possible, do I use 5-30 or 15-40?
The answer from Penzoil was ?? the 15-40 will give the longest engine life.
Now all of the above is a moot point for most drivers that change cars every few years, but for what it is worth ?? they you are.
