We design MR12 fuel to make maximum power in four stroke dirt or street bikes with stock or mild modifications. This is VP’s best fuel yet for 4-stroke applications that can tolerate lower octane values. MR12 has met fuel rules for AMA Pro/Am, CCS, WERA, NMA, WORCS, SCORE and Best in the Desert, as well as club level racing and more. As regulations are ever changing, we recommend checking with tech to be certain.