The spreadsheet has been in wide circulation in the fleet sector, and makes fundamental errors in its calculations of the savings achieved by running LPG-cars, compared to petrol or diesel models.
Programming faults mean the software fails to take full account of the grants available through TransportAction PowerShift to subsidise the additional cost of converting a vehicle to run on gas.
Instead, it multiplies the grant by the proportion of time a fleet can expect a bi-fuel vehicle to run on gas, so if a fleet expects a vehicle to run on LPG 50% of the time, the spreadsheet only gives the fleet the benefit of 50% of the grant. In reality, fleets receive 100% of the benefit of the grant, even if the vehicle never runs on gas.
Consequently, the formula makes gas-powered cars less financially attractive than their true position, potentially deterring green minded fleets from going for gas.
The issue was brought to attention by Lesley Smallwood, who administers the 100-strong fleet of Douwe Egberts Coffee Systems. She had conducted detailed research into the benefits of adopting gas-powered cars, only to have her original cost saving expectations dashed by the spreadsheet, supplied by Vauxhall. So she turned to her fuel card supplier, ARVAL PHH, only to receive exactly the same spreadsheet.
Undeterred, Smallwood then turned to Douwe Egberts' leasing supplier which identified the error in the calculator.
Nick Verney, Douwe Egbert's purchasing manager, said: 'Like all prudent fleet people we are looking at dual-fuel cars. It would appear that most fleet suppliers use this model to calculate savings from gas, but if fleets rely on it no one is going to take LPG because it just does not appear to pay its way.'
Eric Westlake, Vauxhall alternative fuel consultant, said the calculator was an old version that had since been corrected.