I e-mailed Red Line customer service to ask if there was any risk to damaging my catalytic converter (2010 RK Classic) by using their V-Twin oil in the crank case. Zinc and Phosphorus, which are primary additives in most all synthetic motor oils, can possibly damage catalytic converters. Red Line responded to me in less than 24 hrs. (awesome customer service!) and I thought I would share their response here with you people: "Thank you for contacting Red Line Oil, the phosphorus level in our V-Twin Motorcycle Oil shouldn’t cause an issue with catalytic converter deactivation over the typical motorcycle lifespan and average oil consumption. If you are concerned the 20W50 Motor Oil would be a good choice with reduced phosphorus levels compared to the Motorcycle Oil but still substantial for anti-wear protection of your engine." So there you have it! No mention of the zinc though(?). Are there any petro-chemical experts out there that can chime in?