Biodiesel Explained: What It Is and Whether Your Car Can Handle It

With fuel prices climbing, alternative options like biodiesel are getting more attention. But there's a lot of confusion about what it actually is and which vehicles can safely use it. The short version: biodiesel is not just strained cooking oil, and it's not a drop-in fuel for every diesel engine.

Biodiesel is made through a chemical process called transesterification, which removes heavy glycerin from fats and leaves a combustible liquid. That's different from raw vegetable oil, which is too thick and can turn into sludge in a standard engine. Regular diesel comes from crude oil; biodiesel comes from organic plant or animal fats.

Can any diesel engine run on it? Not really. Older trucks with mechanical fuel injection, think pre-mid-2000s models like an old Ford Power Stroke or early Cummins, can handle higher blends because their systems operate at lower pressures with looser tolerances. Modern engines, however, use high-pressure common-rail systems that push fuel past 30,000 psi.

Most automakers say their newer engines can only handle up to a B20 blend, meaning 20% biodiesel and 80% petroleum. Going beyond that risks injector failure and severe pump wear.

There are other trade-offs. B20 often costs the same at the pump as regular diesel, but it has slightly less energy per gallon, so you'll burn more of it for the same distance. Expect a 1% to 2% drop in fuel economy and a small loss in power, especially when towing.

Biodiesel also acts as a solvent, which can dislodge years of built-up sludge in older fuel systems and clog filters within the first few hundred miles. It absorbs moisture and can develop microbial growth, with a shelf life of as little as three months compared to up to a year for standard diesel.

Availability is limited. You'll find B20 pumps mainly in states with strong agricultural ties, like Iowa, Illinois, and Minnesota. Elsewhere, you may need to seek out specialized truck stops. In colder regions, blends are reduced in winter to prevent gelling.

Making your own biodiesel is possible but highly dangerous. It involves handling methanol and lye, boiling waste oil, and managing a chemical reaction that can explode, burn skin, or release toxic fumes. It's not a weekend project.

On the environmental side, biodiesel burns cleaner at the tailpipe, cutting unburned hydrocarbons and soot. But growing crops for fuel uses water, fertilizer, land, and diesel-powered equipment, so the net carbon benefit is smaller than it appears.

For most drivers with modern trucks, the risks, warranty concerns, injector damage, lower efficiency, and short fuel life, likely outweigh the benefits. Unless you own an older mechanically injected vehicle or run a fleet with maintenance staff, sticking with standard diesel is the safer choice.