Harley Davidson Forums - Royal purple

DJM, there's extreme hype that revolves around Amsoil, perpetrated largely by their dealers, which consist largely of anyone who wants to be one and pays the small fee. Amsoil is rarely seen in stores and sells using a pyramid marketing strategy (not pyramid scheme) like Amway. Nothing wrong with this, but some elevate the product to the status of a religious icon. The Amsoil test was conceived, commissioned, and paid for by Amsoil--and there are other truly independent tests (Amercian Iron and Motorcycle Consumer News magazines, among others) that show Amsoil to be a decent performer, but not the miracle oil proposed by the Amsoil tests. Amsoil's promotions revolve largely around this test, and I doubt if you'll find other tests mentioned on their website. The Amsoil test does not measure moly disulfide, which is perhaps the best anti-friction additive and seen in few oils because it is expensive. American Iron magazine said that any oil containing moly shows that the manufacturer cares about your machinery. Since Amsoil's test does not show moly content, I can only assume that Amsoil contains none. I believe M1 contains moly, and oil tests I've conducted show that RP contains >100 ppm.

I've personally seen wear-ball tests conducted where RP greatly outperformed Amsoil, M1, and other oils--even though the Amsoil test shows Amsoil to be the #1 contender in that category. I can arrange to have this test performed for anyone on this forum who would like to travel to Baton Rouge, and you can bring your own samples.

I've used Royal Purple for about ten years in turbocharged cars and two HD's, the last HD going 106k miles before I traded it in. That bike had 158/158 compression, used no significant oil between changes, and never had the heads removed. Could Amsoil do as well? Maybe, but will you keep your bike this long?

That said, I don't push RP as a cure-all, but an excellent oil among many other options. It is very popular among racers of all types (MC, auto, boat), which they claim gives them better performance and fewer tear-downs.

Buy from the usual suspects (Royal Purple, Amsoil, Mobile 1, Redline, etc.) based on availability and price--and wave off the hype. Most will find M1 15w50 to be the best choice, as it is available almost anywhere and is an excellent product. Your choice does not need to be motorcycle-specific. I use RP because of its racing record, my own experience, the fact that I buy it from a distributor at dealer cost, and he delivers it to my door.