What can analyzing my diesel fuel tell me? Distillate (diesel) fuels are organic in nature. From the time of manufacture (refining) until they are used, diesel fuels will degrade. Testing and analyzing fuel deliveries can alert the buyer to the quality of diesel fuel being purchased. Sampling and analyzing on a regular basis allows customers to track stability of their stored diesel fuels and also alert them when contaminates are at unacceptable levels. Many states and accrediting organizations require or strongly recommend testing at least annually. Back To FAQs