Your oil tank has nothing to do with pre-mix. You want to run 32 :1. This means that you need to mix oil with your gas. Get a Ratio-rite. It's a measuring cup that makes mixing a snap. Get it at your local shop or ebay. If you don't want to do this....... steal a measuring cup from your mom or wife. You want to mix 4 OZ of oil to every gallon of gas. So 1 gallon will require 4 oz. of oil....two gallons will require 8 oz. of oil and so on. Don't buy junk oil. Go to a motorcycle shop to get it. Mix the gas / oil in a tank...not your bike. Pour some gas into the measuring cup after you put oil in it then pour it into the tank. Make sure you mix the gas and oil by rolling the tank around. Once the oil and gas is thoroughly mixed, pour it into your tank. Sounds like a pain in the as$ but it's very easy once you get the hang of it.