I've read about being able to just put veg oil in my tank without conversion. What do you think?

This really has grown from the experience of owners of old(er) Mercedes. Whilst it is true that these vehicles are particularly veg tolerant, primarily due to their very robust Bosch injection system design and non-direct injection topology, certain key points should be borne in mind:

1. Veg oil allowed to cool on injectors. If a fuel injector is allowed to cool with veg oil remaining on it, 'caramalisation' can occur. This is where a hard lacquer type build up can occur on the injector, leading to a compromised spray pattern. As well as affecting performance and raising emissions, this can also cause non-atomised veg oil to hit the engine cylinder walls -especially so in direct injection engines. Here it can form what is often termed `knacker lacquer` a hard layer of unburnt oil that can lead to piston ring damage. Starting up and cooling down on diesel (i.e. twin-tank solutions) are an excellent way of ensuring the injectors are kept cleaned by using the detergents added to in mineral diesel.

2. Increased engine & pump stress. Put simply, the engine wasn't designed to start up on veg oil. In winter, when veg oil viscosity is particularly high, a huge increase in strain is placed on the injection pump internals. This will inevitably lead to a reduction in the component's life. Additionally, the poor vaporisation of cold veg oil means an engine must crank over for longer, putting an increase strain on the starting motor and battery.

We certainly therefore do not recommend this in modern cars. If you have an old Mercedes, and don't intend to run it for more than a few years, then you may consider going this route - but be warned...

Got a question we've not answered? Contact us