I am a Tech at a dealership in oregon, a lot of shops will try to sell you the HD oil instead of another brand simply because that is really the only thing we can suggest, since we are backed by Harley. However using another brand oil (as long as it meets or exceeds harleys requirements) will not void your warranty, but if i could make a suggestion, stick with the harley oil, i deal with different oils all day, everyday and Harley is the one that myself and all the other techs that i work with use. a lot of the other oils that people think are "superior" are just the opposite, and many of them are very thin in viscosity. so anyways, i hope that helps you with your dilema. good luck.