THE residual value gap between single-fuel and bi-fuel vehicles is closing, according to Glass's Information Services.

The vehicle valuation and market intelligence specialist says that whereas 12 months ago it was predicting a petrol/liquefied gas car would be worth £300 less than a similarly-specified petrol model after three years, demand on the used market for LPG was having a balancing effect on 'clean fuel' residual values.

Bill Carter, editor of AutoProVision, Glass's residual value forecasting system, said: 'Retail customers lead the used market and they are becoming increasingly aware of the cost-saving benefits - if not the environmental benefits - of gaseous fuel to the extent that when the first three-year-old bi-fuel cars appear for resale we don't see there being a disadvantage.' He added that the public needed more information on clean fuel technology and the refuelling infrastructure for gaseous fuels had to grow significantly to drive values up further.

Glass's does not yet publish residual value predictions for bi-fuel vehicles. CAP Motor Research does - and remains pessimistic.

CAP Monitor editor Mark Norman said: 'Until there's a massive improvement in the infrastructure, they don't stand a chance and by the time that's in place we will probably have a better road fuel alternative. 'On top of that, there are still concerns about the reliability of bi-fuel vehicles, based on information from countries which have been operating gas fleets a lot longer than Britain.'