It really depends, with the Kymco autolube pump you can adjust the amount of oil injected by tightening the 12mm lock-nuts. The existing oil injection is more than enough for a street 70cc build. You only need to go premix if you plan on building a motor that will see more than 12,000rpm on a regular basis. I premixed my Zuma a while back and won't again, I drove it a lot and was going though about 3 bottles of 2t a month. It took about a quart to mix 5gal and I could go though that in a week or a week and a half, gets expensive fast. While injection goes to 100:1 at idle and saves a lot of the good stuff.