1 can of torco Mach series should be used with 15 gal on 93 which will yield a 100 rating. I would NOT stack 2 bottles! There is a PDF on the torco site for mix ratios, I'm on my phone doing the reply so I can't add it to this thread, but just don't do it. This additive (and NOS Octane boost) contain MMT and you don't want too much of that in ur engine. Pull one of ur plugs and that will tell you why. Mix Sunoco 104 with 93 or use 1 bottle of torco... Be safe.