A recent visit to the supermarket gave me a cheeky idea about how to beat the spiraling cost of fuel.

Here in darkest Oxfordshire, diesel is already pushing £1.08 a litre, with the RAC warning that it will be peaking somewhere north of the £1.10 mark once the seasonal Christmas peak has done its worst.

A trawl around the shelves proves that fuel therefore now costs more than Perrier water (95p/litre), Coca Cola (75p/litre) or Tesco own-brand 'Strong Cider' (93p/litre). None of which, sadly, is quite potent enough to run a car on.

But then it struck me - one thing in the store would be up to the job.

Remember all that hoopla about running older diesels on used cooking oil from a few years ago? Great in principle, but it relies on both securing a ready supply of the stuff from your local chippie (the proprietor of which probably has a Citroen ZX 1.9D parked outside for this very reason) and also the ability to filter the deep-fried nasties out of it.

But the surging fuel prices mean that it's now possible to get proper, off-the-shelf vegetable oil for less than the cost of a litre of diesel. Tesco's best offer of six litres for £5 works out at 83p/litre - I'm sure wholesalers would do better - and an older and less-fussy diesel car will accept that as a direct substitute for DERV.