You can run 16% you may have to lean it 1/16 out for the same exact performance as 20.I was told by the owner of my lhs is the higher the nitro content,is just crazy.They are all the same you're just paying more and wearing the engine fast+ there's always that chance of breaking it unless you use extra shims in the head.When you can get the same performance for less money by simply ajusting the high end.I belive it to a point but i just use 20% also Odonnell speed blend.But i wouldn't hesitate to run 16 through it,wouldn't hurt it that's for sure.More lubricant.