The funny thing about techs and mechanics is that if you ask two mechanics, you sometimes get three opinions . . .
Here is mine: a motorcycle engine is one of the most abusive, as far as oil is concerned. You have to lubricate the crankshaft, rods, pistons, cams, etc., all the normal stuff. In addition, you have to lubricate a gearbox, which would be better served with a heavier oil, like what you might put in the rear end of a car. Then you have to lubricate the clutch. The hardest component - in regard to oil - is the gearbox. Gearboxes tend to "shear" the oil when the gears mesh, breaking it down. In addition, you have material from the clutch getting into the oil, and combustion byproducts. Petroleum based oil will break down at around the 2,000 mile mark. That is when it starts to lose it lubrication qualities. Synthetics - as we all know - can go 10,000 miles before you may have to be concerned about it breaking down. But ANY oil - even $100/qt oil from the space shuttle - will get contaminated in a motorcycle engine over a period of time. It will get combustion byproducts in it, it will get condensation in it, and it will get friction material from the clutch in it. Your oil filter will not filter out all the contaminants that get into it. If you ever sent oil to a lab to be evaluated, you would probably be shocked as to what can end up in oil over time. In short, it won't break down, but it will get DIRTY . . . and that is why it needs to be changed. I urge my customers to change their oil every 2,000 miles for petroleum based oils, and every 3,000 miles for synthetics. I don't really care what my Amsoil rep says - he is just trying to sell oil. Changing your oil is cheap insurance to protect a motor, especially a high performance motor . . .
