I've done some poking around this forum and found these questions popping up often. Frankly, I can't get straight answers on them. This may be a futile attempt to get answers but I thought I'd try... 1) Does oil color indicate anything about engine health at the end of the OCI? Common sense dictates if the oil is as clear as when it was put in that the engine is either spotless or the oil isn't cleaning the mess that is in there. 2) If the additive packages in oils control the cleaning of the engine, why are synthetics generally considered better at this? Is it simply that the higher price justifies more additives for synthetic oils? 3) Since each oil will be different from the next, why would anyone recommend a general synthetic over a general conventional? Wouldn't the best conventional oil beat out the worst synthetic in terms of performance? (this is assuming synthetics are generally considered superior to conventional oils - which I realize is controversial around here) 4) Do synthetic oils give a film that stays on the metal parts? Is this why startups are supposedly easier with synthetics? Why don't conventional oils do this? 5) Does an oil type like 5W30 imply the oil is thinner at lower temps and thicker at high temps? Or is it the other way around? Thanks for the info.