Biodiesel blends mix petroleum diesel with biodiesel made from vegetable oils, animal fats, or recycled cooking oil. B5 means 5% biodiesel, B20 means 20%. While biodiesel reduces emissions and supports renewable energy, it introduces challenges: worse cold flow properties, faster oxidation, higher microbial growth risk, and potential injector deposits. Fuel additives like Fuel Ox are formulated to address all these biodiesel-specific issues.