B5

B5 is a diesel fuel blend containing 95% petroleum diesel and 5% fatty acid methyl ester (FAME) biodiesel by volume. It is used in compression ignition engines without modification to the engine, fuel system, or emissions control equipment. The biodiesel component is typically produced from vegetable oils, animal fats, or waste cooking oil through transesterification.

B5 occupies a middle ground in the biodiesel spectrum. Pure petroleum diesel is called B0; B100 is pure biodiesel. The 5% threshold is significant because it is the maximum biodiesel content permitted in most original equipment manufacturer (OEM) fuel specifications for standard diesel engines without voiding warranties or requiring hardware changes. Engines built to EN 590 diesel standards in Europe and ASTM D975 standards in North America tolerate B5 without issue.

Compatibility and practical limits

The 5% biodiesel content raises the cetane number of the blend slightly and improves lubricity compared to B0, which benefits fuel injectors and pumps. However, biodiesel absorbs water more readily than petroleum diesel, and it can degrade rubber seals in older fuel systems. B5 blends also have a higher cloud point (the temperature at which wax crystals form), reducing winter performance compared to B0, which matters in cold climates. Storage stability is shorter; B5 can oxidize within six to twelve months if stored in conditions that expose it to heat, light, or air.

Regulatory mandates drive B5 adoption across the European Union, many U.S. states, and other markets as a renewable fuel requirement. Since the early 2000s, biodiesel blending has been a cost-effective way to reduce tailpipe emissions and petroleum consumption while using existing supply chains and engine technology. However, the jump from B5 to higher blends like B20 typically requires OEM approval and sometimes hardware upgrades such as fuel hoses rated for biodiesel compatibility.

B5 is also known colloquially as a 5% blend or super diesel in some regions. It differs from conventional diesel primarily in feedstock composition and handling rather than performance; most operators will not notice operational differences at the 5% blend level. However, fleet managers must monitor fuel supplier quality and storage conditions, because contamination or poor blending can cause fuel filter clogging or injector deposits.