I use Mobil 1 synthetic 5w-30 in my integra. I noticed alot of people use 10w-30. I know it probably doesnt make a big difference between the two, but dont honda's come with 5w-30 from the factory, and isnt it recommended also? I'm just basing this on what I learned in school. They say when a auto co. recommends a specific type of oil, its because of the little pores or oil passages in the engine, and that if the oil used is to thick, than the oil would not pass through as smoothly, therefore the engine/engine parts would not be lubricated as well. Is this true? And what is the Mobil 0w-40 for...an employee at the store told its to be used with new cars...(sure)