Biodiesel: How It Works and What B20 Means for Your Diesel Engine

What Is Biodiesel?

Biodiesel is a renewable fuel made from vegetable oils, animal fats, or recycled cooking oils through a chemical process called transesterification. The output is fatty acid methyl esters (FAME) that closely mimic petroleum diesel in combustion properties. It can be used in any diesel engine without modification at B20 (20% biodiesel) and below.

Blend Levels

• B5 (5% biodiesel): Widely used, virtually undetectable by engines, approved by all major OEMs
• B20 (20% biodiesel): Most common fleet blend, mild power reduction, approved by most OEMs, widely available
• B100 (pure biodiesel): Requires engine modifications for cold weather and may affect warranties

Fuel Economy Impact

Biodiesel has approximately 8% lower energy content per gallon than petroleum diesel. At B20, this translates to approximately 1.5–2% MPG reduction. However, biodiesel's higher lubricity improves injection system efficiency and reduces friction wear — partially offsetting the energy disadvantage. Most B20 users report 0–1% net fuel economy change versus petroleum diesel.

Emissions Benefits

B20 reduces particulate matter by 10–20%, CO by 15%, and HC by 10% vs petroleum diesel. NOx may increase slightly with some biodiesel formulations. These emission reductions are particularly valuable for fleets operating in urban environments with air quality regulations.

HHO + Biodiesel

Biodiesel and HHO complement each other. HHO's combustion improvement compensates for biodiesel's slightly lower energy content, while biodiesel's clean-burning properties reduce the deposits that HHO supplementation helps address.