265k miles and counting..
Joined: Jan 2003
Location: Tampa Bay Area
The thing you have to remember is that a modern 4 cylinder engine is not a small blcok V8 from the 50's-80's. The internal tolerances are MUCH tighter and specifically designed for low viscosity oils ( some as low as 0W-30!). Running too thick an oil could starve the bearings because it is not able to pump it in the bearing clearences. If you are concerned about lubricity and film strength, a good synthetic like Redline , Royal Purple or Mobil 1( my favorite) will take care of that , and give you much longer service life.I have 225k on my Frontier and run 5W-30 all the time. No problems at all.Plus, the lower viscosity oil will use less gas and have less parasitic drag inside the engine. The only way I would run a thick oil is if the engine was old and the bearings tired, so that I could push it a little while longer before a rebuild. So, save the 40 weight, 20W-50 etc for the smoking 305 in your 1987 Caprice wagon, because that's the ONLY place it belongs.
1998 Nissan Frontier XE/2wd/5spd 1 owner, 264k miles
1985 Olds Cutlass, 350 Chevy, owned for 14 years
WANTED: 1968-1973 Datsun 510 or 1991-1994 Sentra SE-R
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Last edited by himilefrontier; Sep 10th, 2005 at 11:30 PM.