If you like the Castor smell drop in an ounce to your mix. That's all it takes to give you that 60s go-kart smell. I like to get home from a ride and park the bike in the garage and get that Castor aroma. It also seems to catch up to you at stop signs. Opti-2 @ 100:1 with an ounce of castor per gallon. The best of both worlds.