 Diesel Fuel Cetane Levels In many states, the Cetane rating in diesel fuel is 42 to 45. Most diesel engines operate more efficiently with a Cetane rating of 48 to 50. One treatment of Hot Shot Secret Diesel Extreme will raise your Cetane 7 points, increase fuel economy, and improve cold starts. Due to a cleaner burn, there are less hydrocarbons and particulate matter in your exhaust.