Oil viscosity - more difference than I would have thought

[i-DSi]

Don't forget one of the most important things to let an engine run on 0W20 is an oil pump with a high flow on low revs (in combination with the narrower tollerances).
Bowtie, I don't really understand what you mean with 'it's possible some manufacturers use 0w20 to achieve better EPA estimates and fewer emissions, but at the expense of lubrication.'. I assume you talk here about the fact that a thinner oil does not perform as good as a thick oil at very high temps in combination with high pressure? But these circumstances do not occure that often. What does occure at every cold start is that a thick oil is by far not as fast where it needs to be than the thin oil. So lubrication might be better in real life with the thin oil.

[bowtieguy]

a true synthetic 0w30 is just as good at start-up as 0w20, but's it's FAR superior in lubrication, longevity, heat protection, cold weahter performance,etc. what i'm suggesting is that manufacturers use the cheapest methods available to achieve certain #s, irrespective of the interest or longevity of the vehicle.

remember toyota's recent issues? to be fair, shortcuts(and cost cutting) has affected several auto makers in recent years.

edit: 0w20 is likely fine for winter/cooler climates.