another thing that noone seems to have hit on, is the fact that if you use synthetic oils, you have no need to change it every 3000 miles. i have ran amsoil in my cars and bikes for the last 3-4 years. this last oil change on my car, a 2004 dodge stratus R/T, was 23,000 miles on the same oil. it came out looking like oil that had been in a car for 2,000 miles. every single bike i've put amsoil in, the transmission instantly shifted smoother, took longer to get warmed up, which in my eyes means theres less friction and more cooling inside the engine, and even got better gas mileage.
i even left a dirty towel sittin next to the case of amsoil i'd bought, walked out to the garage the next day, and the towel was clean, folded, and a hershey's kiss on top of it! did the oil do that??????