How hard can it be to drive coast-to-coast across Britain on one tank of fuel, they asked? Not very, we said. So we topped up, left Great Yarmouth on the east coast of England and headed on a road trip to Anglesey on the west coast of Wales. The idea was simple: drive across the UK and splurge all the leftover petrol on some hot laps of the Anglesey race circuit.

Our job was made easier by being in a Toyota Auris Hybrid, the only volume hybrid car manufactured in Britain and one theoretically capable of travelling more than 70 miles on every gallon of petrol. And to make us eke out every last drop, we brought along one of Britain's hyper-miling experts Karl Dyson to teach us some eco-driving tips.

Watch our video diary above - and if you correctly guess how many laps we managed at the track before we ran out of petrol, you could win six months' worth of free fuel yourself! To enter, click 'Add your comment' below and post your estimated number of laps of Anglesey's shorter 'Duck' circuit plus one eco-driving tip in less than 50 words as a tie-breaker (we've posted an example as the first comment below).

You're each allowed one guess and we'll use the tie-breaker in the event that more than one of you correctly guesses the number of laps. Toyota will provide a prepaid Visa card charged up with £437, the fuel cost of driving 5000 miles in an Auris Hyrbid.

This topical competition closes at midnight on 1 June 2012. Naturally there are a few Ts & Cs with this kind of comp, so click here for the full terms and conditions. Calculators ahoy and good luck with your guesses!