I ride a 98 XCR 440 SP, and i have always used to the Polaris VES oil as well. I have used AMSOIL in the past with excellent results, but is also expensive. The key to these oils i believe is to prevent sticky valves and does that by burning cleaner. The synthetics have little or no ash and other substances that cause stickiness. I have also never fouled a single plug using the AMSOIL. Coincidence? Maybe. How often do you clean your valves??? 500 miles or less has worked for me.