If the fuel is very volatile, it refers to the fact that it can be easily vaporized. The volatility of the fuel can affect how easily the car will start, warm up, and how well it will run. As you might know, there are two different grades of diesel fuel that vary in their volatility. Automobiles and smaller vehicles use diesel with greater volatility as the fuel makes them more responsive. On the other hand, larger vehicles like trucks use lower-volatility diesel to ensure better safety and stability.