We ran a mix of VP C12 and pump gas all last year. We mixed 50/50 and it worked well for us. Some have told us it's not really the right way to do it, but for our deal (BBC blown, 6% over driven 28 degrees timing) it seemed fine. We were told by many not to use av gas too for similar reasons. We also ran a 50/50 mix of F&l with good results and it was half thr price of C12, however when we tried to run 100 F&l we had a flat spot out of the whole and top end didn't feel very good. Probably needed more timing or jetting. This year we will be running 100% C12 as we have bumped up the blower and timing, got to keep it interesting.