I hate to get off our favorite sport ofsquid bashing, but I think every 2500 miles is about right. A mechanic whose judgement I trust thinks you can safely go twice as far on synthetics, which is only fair, since they cost about four times as much. Whatever you use, be sure it's formulated for motorcycles. I used regular engine oil (20-50 here in California) for many years, but I'm told the clutch, which runs in an oil bath, needs slightly different properties, and the oil in a motorcycle also is subjected to greater shear type of stresses in the gearbox than would be encountered in a car engine. Now, back to disrespecting that idiotic squid.