if your happy with 5% then stick with it. Your engine will not make any more power on anything more than 15%anyway. For a type of fuel i generally use 10% or 15%. the two brands i generally use are Wildcat or Omega. This year i will try some Powermaster. with a castol/synthetic oil mix your engine will run a long time. To the Moron that said to use 33% nitro fuel. Let's see no extra power with your engine, more wear and tear on your engine,about 5.00 a gallon more. Yes indeed i can see why he wants you to run that fuel he sells engines.