Quote:
Originally Posted by jparnes1
With all due respect, I'm not sure you understand what the viscosity numbers mean. The first number is the oil's maximum viscosity and flow at a cold temperature (at start up). The second number is the maximum viscosity and flow at hot temperatures (normal operating temps). This means that 0W-40 is thinner at start up for better flow when it's cold and thicker at high temps for better wear protection compared to 5W-30. Does it really make a difference? I doubt it but that's what I use.
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I have tried both in the past and the 5w operated quieter and smoother at operating temp. it fills your bearings better. Yes, I know that the 5/0W stands for its flow on start up.
but a 0W is overall thinner then a 5w. theres no magical chemistry at play here, an overall thinner oil will not protect your engine as well as a thicker one would. if the W weight only applies for cold weather, why is there such a big difference between the two, *even at operating temp*
Like i told the other guy, I strongly suggest you read up on the north american CAFE Requirements. you will note that ONLY north american spec'ed engines, and not a single other place in the world requires a 0w oil. even russia, with its frigid temperatures still spec's a 5w.
your engine isnt going to be running cold forever. I am simply giving you a heads up because BMW's have looser bearing clearances (to run thicker oil and thus therefore protect critical parts like rod bearings better) and also control oil temperature more effectively.
http://syntheticperformanceoil.com/s...es/5w20oil.php
if you are interested in learning more about the CAFE requirements, here is a great starter link.