FAME versus NERD is not the latest summer blockbuster for teens. FAME and NERD are the acronyms defining the two main forms of biodiesel—a non-petroleum renewable fuel that can theoretically run in any diesel vehicle without modification.

Why is it important to know the difference between FAME and NERD? Because they are not created equal in the eyes of automakers when certifying the use of biodiesel. Even though both methods produce a fuel to displace petroleum diesel, not every automaker gives the thumbs-up for their cars and trucks to be used with B5—a blend of 5 percent biodiesel and 95 percent petrodiesel.

Volkswagen, Mercedes-Benz and Ford generally are okay with B5, while Chrysler and GM approve B20 for some of their trucks. The other automakers have been very quiet about biodiesel—a stance that’s due to change as new diesel vehicles come to the market in the next few years.

Biodiesel advocates are pushing for warranty protection for stronger blends up to B20. Some cite the Magnuson Moss Warranty Act Engine, which holds manufacturers responsible for warranty protection, regardless of the type of fuel used—unless damage is directly caused by the fuel.