 Diesel Fuel Zetane Levels. The Zetane rating in diesel fuel is 42 to 45. Most diesel engines operate more efficiently with a Zetane rating of 48 to 50. One treatment of Hot Shot Secret Diesel Extreme will raise your Zetane 7 points, increase fuel economy, and improve cold starts. Hot Shot Secret Diesel Extreme is available nationwide at truck stops, fine farm and auto stores, and online at hotshotsecret.com. Hot Shot Secret.