IF THE CAR IS NOT AS DESCRIBED then you can demand a refund,iirc this comes under the sale of goods act. if there are no faults with the car,then it comes down to your research or lack of it. i had a 2ltr petrol and to be honest think the most i got out of it was around 25 to the gallon,NEVER AGAIN. count your self lucky you havnt got a v6,mind you it gets you there before youve even left. :)