Straight vegetable Oil (SVO)

In stead of chemically modifying vegetable oils to form biodiesel several systems have been conceived to use these oils directly as a fuel. Main problem is that vegetable oil is much more viscous (thicker) than conventional diesel fuel. It must be heated (thinned) so that it can be properly atomised by the fuel injectors. If it's not properly atomised, it won't burn properly, forming deposits on the injectors and in the cylinder head, leading to poor performance, higher emissions, and reduced engine life. This can also happen with unsuitable oils, for instance those with a high iodine value (unsaturated fatty acids), such as linseed oil, form tough epoxy deposits, not good for engines. Furthermore many oils have the undesired property of crystallizing at low temperatures forming waxes which clog up the engine.

However all these problems can be overcome by making some commercially available adaptations to the engine. So far one engine has also been specifically designed for burning vegetable oils, the so called ELSBETT engine, multi-fueled, 3 cylinder, oil-cooled engine with direct fuel-injection and an integrated injection system (unit injector process).