EXCLUSIVE research by Fleet News shows fleet managers need to investigate the case of every driver receiving free fuel for private mileage to determine the value of the perk. First the average economy of each vehicle must be checked and secondly, the price of fuel is calculated, for which we have used the average figures printed each week in the.

Then the driver's higher rate tax band is needed and the full set of fuel scale charge figures for 1999/2000 and 2000/2001. The fleet manager multiplies the relevant scale charge due by the tax rate in percent.

The amount of tax to be paid is then divided by the cost of fuel, either in pence per gallon or litre, depending how you measure the economy of a vehicle - the result is the amount of fuel paid for by the tax.

Finally, multiply the number of gallons or litres by the mpg/litres per 100km of the car and the result is the rough number of miles needed to break even. For example, a Ford Mondeo 1.8-litre petrol driver achieving the manufacturers stated average of 36.2mpg at £3.55 per gallon, who paid tax at 23% in 1999/2000 would have paid £354.20 in tax, currently equal to 99.77 gallons and needed to cover 3,611 miles to break even if the tax had remained the same this year. This year, the same driver is paying for 173 gallons through tax of £616 and so would have to cover 4,850 for the perk to have been worth it.