http://synlube.com/sae5w-20.htm

Dr. Haas has made me believe that 90% of wear occurs at startup so thinner oil is better. But whats the truth about what synlube is saying 30% less engine life on thinner oil. :dunno:

What do you guys think?

Personaly I would never use a sae 5? I have always used oils in the 20-40 range with no ill effects in the UK.. :)
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SynLube is a crackpot oil. 30% less engine life vs. 5W20. Sure. They offer a couple of pages trying to explain SAE J300. They then say that b/c MB and heavy duty engine mfg use xw40 oil, then xw20 reduces engine life. Oh, and then they say you must use 5w50 which probably has a ton of VII for such a wide spread. It appears to be marketing hype with a mediocre (at best) oil. They offer no SAE studies on engine wear, not even a simple $20 UOA to back up their preposterous claim.

Dr. Haas is correct and is backed by SAE studies that most wear occurs at startup. You simply can't get a 'thin' enough oil for startup.

Dr. Haas has made me believe that 90% of wear occurs at startup so thinner oil is better.
correct. but get real...... engines don't wear out from running any given oil at startup. I've taken apart 100K mile porsche engines that have been beat an ran the reccomended 15w-50 or 20w-50 oil and there is never any measurable wear on bottom end bearings. no camshaft wear, nothing of the sorts.

although correct info, it can't be taken to extremes... there's no reason to put that much concern on that. you're not going to wear out an engine within the rest of the car's life expentancy based on startup engine wear.

I don't beleave any of that. There is just some new oil compony trying to sell you there "special" oil.

HORSEPUCKEY!!!!