I believe Coolpower 4-cycle is 15% nitro and 17% oil (it was the last time I asked them about it anyway) Regular Coolpower 15%also has 17% oil, so the 4-cycle fuel you have will probably work just fine without adding oil, just as Artisan says. But if you just have to have a full 20%, add 4.8 oz of oil. (I add 3.2 oz of Klotz BeNOL to my Coolpower, which brings it up to 19%, because it makes me feel good to do so. Not sure how my 2-cycle engines feel about it.) I believe that Klotz BeNOL, KL-100, and KL-200 will all mix with the Coolpower.