50 w oil

[madmaxx]

The majority of your engine wear occurs in the first 5 minutes of driving, first you cylinder walls are cold, your pistons are hot, soooo, your pistons generate heat due to friction until the block gets to the optimium temp 200f for combustion and clearances between piston and wall are optimized. If your oil is too thick during this time and not lubricate the rings and cylinder wall bingo excessive wear. You are absolutely correct straight is better if you run your engine around the clock and never shut it off, but we drive 15 minutes to work, to the grocery store, hot cold hot cold, you get the picture.

Remeber gm,ford, toyato, etc all warrant their cars for 50K miles and each and everyone use multiweight, most today use 5w20!!! If you were running the indy 500 use the straight weight with an oil pan heater, if you drive lilke most of us use the multigrade.

Originally Posted by sparks

Found this article.This study shows that artificially polymer thickened oil (Multi-Grade)
will tend to have a higher temporary viscosity loss (shear) under load
than an oil who's base is the same viscosity (straight weight oil). In
otherwords, multi-grades tend to fail, break down, loose viscosity when
it is needed most... under load, whereas a straight weight oil will not. This sounds like its sayin that multi grade is inferior to strait wght oil ?

http://resources.metapress.com/pdf-p...0&size=largest