ADAC Warns Against Using Plant or Heating Oil in Diesel Engines

The German automobile club ADAC has advised drivers against filling their diesel car tanks with vegetable or heating oil, despite high fuel prices. Experts at the organization explain that neither cooking oils nor heating oil are suitable alternatives for vehicle tanks.

The primary issue with vegetable oils is their significantly higher viscosity compared to diesel fuel. ADAC experts state this can lead to starting difficulties and negatively impact engine performance and lifespan. Modern diesel vehicles' injection systems are not designed for the thicker vegetable oil, causing inefficient combustion and potential long-term damage to the engine and fuel system. Deposits can also form in filters and fuel lines.

Furthermore, using heating oil as fuel is legally prohibited in Germany due to its different tax classification. Technical problems can also arise from a lower cetane number, potentially causing engine knocking, reduced performance, and increased soot emissions.

ADAC notes that while older diesel engines with lower injection pressures might run intermittently on vegetable oils, it still shortens their lifespan. Converting an engine to run on vegetable oil would necessitate modifications costing between approximately €1,500 and €5,000, including installation.