A buddy is trying to decide whether to use synthetic oil or not, so he asked a dealer what he thought and the dealer said not to use it. He said that the stuff is TO slippery and instead of a bearing rolling they will slide and creat a flat spot. But in the same breath he told my friend he was taking delivery of a bike with synthetic in it from the factory. Needless to say the dealer has my friend flam boozeled and will not be using synthetic, but instead he will stick with Harley oil to be safe. To each his own.