So was M1 15w-50. Says it right on the bottle. The advantage you get with RL is that you could run a lower viscosity then the M1 50wt and still have an oil that is robust for racing. M1 15w-50 has more ZDP for racing then the other grades of M1. With RL, it's consistant across the board. RL is also the most shear stable oil out there.