 At Hot Shot Secret, we share the science behind common diesel problems and their solutions. For example, diesel fuel C-Tain levels. In many states, the C-Tain rating in diesel fuel is 42 to 45. Most diesel engines operate more efficiently with a C-Tain rating of 48 to 50. One treatment of Hot Shot Secret Diesel Extreme will raise your C-Tain seven points, increase fuel economy, and improve cold starts.