Will smartveg work on a common-rail engine?

The short answer is 'yes' but please read some of the following concerns that are often raised. The major issues associated with common rail engines are mainly (but not exclusively) the following:

1. Insufficient lubrication: Even when hot, the viscosity of vegetable oil is higher than that of standard diesel. This leads to an increase in drive power required for the injection pump which may shorten the life of any pump drive belts etc.

In terms of pump and injector wear, the lubrication properties of a fuel becomes an important factor in the life of the pump, particularly in high pressure systems. This has led to expensive development and manufacturing exercises to get injection pumps to work with some fuels. For example, with pumps designed to cope with methanol, all bearings or bearing surfaces are made from pure carbon or carbon composite materials.

Diesel pumps are typically made from a mixture of iron and stainless components hardened to levels that endow them with suitable service lives but with minimal running clearances. These then require a source of lubrication supplied by some of the compounds in the fuel itself or its additive pack.

The problems of lubrication can be summarised by looking more closely at the fuels involved; methanol has almost zero lubrication properties and can act as a seizing agent for normal materials by enhancing the galling properties of several base materials. Petrol is better than this but still effectively cleans off any residual lubrication film from the contact surfaces. Diesel is better still, as it does possess some limited lubrication properties, and does meet a loose specification to cover this aspect. Vegetable oils (recall Castrol R - the famous castor oil based lubricant) do contain compounds which have notable lubricant properties, and a limited percentage of these will also have much lower viscosities than other compounds in the oils. Hence it is likely that the lubrication properties of these oils will be an improvement over base diesel.

2. In-tank lift pump: some common rail engines have done away with with mechanical, engine mounted lift pumps and replaced them with electric pumps, located in the vehicle's fuel tank. These unfortunately have shown themselves to be unreliable and prone to failure on veg oil, due to the viscosity of the cold oil. With vehicles of this nature we recommend running the vehicle with veg oil in the auxiliary tank with a veg tolerant pump feeding the high pressure pump in the engine bay.

3. Injection pump inlet pressure requirements: on those vehicles with electric lift pumps, it's not uncommon to find that the vehicle's ECU will not allow the engine to operate if the inlet pressure falls outside a narrow band of allowable pressures. It's therefore necessary to replicate this pressure range with the veg oil input. This is beyond the skill range of all but the highly experienced DIY'er, so we recommend that you allow one of our fitting centres to undertake this for you.

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