Heat exchanger and additional fuel tank to run biodiesel

Most diesel car engines are suitable for the use of Straight Vegetable Oil with certain modifications. Principally, the viscosity and surface tension of the SVO must be reduced by preheating it, typically by using waste heat from the engine or electricity, otherwise poor atomization, incomplete combustion and carbonization may result. One common solution is to add a heat exchanger and an additional fuel tank for the diesel or biodiesel blend and to switch between this additional tank and the main tank of SVO.

The engine is started on diesel, switched over to vegetable oil as soon as it is warmed up and switched back to diesel shortly before being switched off to ensure that no vegetable oil remains in the engine or fuel lines when it is started from cold again. In colder climates it is often necessary to heat the vegetable oil fuel lines and tank as it can become very viscous and even solidify.

Single tank conversions have been developed and have been used throughout Europe. These conversions are designed to provide reliable operation with vegetable oil. Modifications to the engines cold start regime assist combustion on start up and during the engine warm up phase. Suitably modified indirect injection (IDI) engines have proven to be operable with 100% SVO down to temperatures of  −10 °C. Direct injection (DI) engines generally have to be preheated with a block heater or diesel fired heater.. For long term durability it has been found necessary to increase the oil change frequency and to pay increased attention to engine maintenance.