quote:
Originally posted by Dave Sherman:
So far, we have UOAs that say 5W-20 is fine, we've got the manufacturers saying it's fine, and we've got a handful of amateurs saying it's awful just because they think so. Sorry, I'm an engineer, and I believe numbers and the folks who built the car more than "gut feelings". If Accord is terrified of 5W-20, fine. It's his car. He just seems determined to find every shred of anecdotal evidence in an attempt to convince the rest of us, but some of us need a little more convincing.
Very well said, Dave. And as a fellow engineer, I too was searching for some hard data back when I bought my 2002 Accord which specs 5w20 since I keep most of my cars for an average of 15-20 years. And they are driven very hard on the back roads in central Texas heat.
Having worked in the defense and automotive industry for many years, I actually had the opportunity to talk to several engine development engineers about my concern with 5w20 oils. And not one of them voiced any concern when it's used where spec-ed since they have plenty of data from severe dyno and fleet tests.
But being the stubborn engineer I am, I still wasn't satisfied and decided to conduct my own tests running everything from thin 0w20 to a thick 10w40 and used UOAs to see if there was any significant difference in wear metals. Result? No significant difference.
My results pretty much mirrored those obtained by user MNGopher in his 4.6 F150 oil test, except my oil consumption remained the same.
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=002975
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=001965
One also has to keep in mind that ~90% of your engine wear comes from cold starts. Thus even with a sub-optimal choice in oil, as long as it's kept uncontaminated and flowing properly, the most you will effect the life of the typical street engine is ~10% with oil selection. This is quite different than a race engine which may see a dozen or two cold starts in it's entire life, and spend most of it's time at WOT.
So...if thicker oil lets you sleep better at night, by all means use it. But let me suggest you look for a better oil, not necessarily the thicker oil.
[ June 20, 2006, 12:50 PM: Message edited by: 427Z06 ]