i use either 10w30 or 20w50 synth oil. the lower weight oil seems to make a tad more power, i guess because the engine has to fight against a lower viscosity, but that gain is neglible. since power is about the same what i want to know is what is happening internally w/ the different weight oils? would a lower weight provide more protection because it can flow more easily thus providing more lubrication, it can get into smaller spaces, heat is more evenly distributed because the higher volume of oil flow. or would higher weight be better because it would have higher oil pressure, and can leave a thicker layer of coating for more protection, and is more heat, wear, and crush resistant. which is better for durability and reliability? who has opened up engines which used different oil weights? which ones looked like they were in better overall condition? would bearing wear be the most important aspect in determining which weight oil to use? how do differences in power output determine which oil is best?

 

Thinner oil (10W-30) would be better in cold climates since it will get flowing sooner and reduce cold-start wear. Thicker oil (20W-50) should offer better protection in warmer climates and when the engine is hot. I think Mobil 1 has some 5W-50 that seems like it should be good both when cold and after the car heats up.

Synthetic is a good thing. I haven't compared engines with different weights, but engines that use synthetic versus conventional oils are way, way cleaner on the inside (oil pan, lubed surfaces). Engines with synthetic often look "clean" and engines with conventional oil have lots of sludge and varnish (I think that's what its called). Changing the filter often (at least with every oil change, more often if you do extended intervals with synthetic) should help keep the oil clean and the wear down, too.

-Max