Ive looked into mpg figures for a while now, and there are much bigger variables besides air con. For example tyre pressures, tyre make/model and compound can make a much bigger difference than having your air con on or off.
As has been previously stated a smaller petrol engine with little torque will be effected a lot more than a bigger diesel engine. Average figures show that air con takes approx 2-4bhp, which on a large 150bhp diesel engine is tiny, but a small fiesta 1.4 with just 70bhp is much bigger.
Tyres is the biggest varibale, but you have to weigh up the cost of the more economical tyre against a cheaper brand. Is paying twice the price for a new michelin going to warrant the small saving in mpg.
I would personally just enjoy the car, switch on the air con without worrying how much its really costing. The saving is so small your not really going to notice it unless your a rep doing 80k+ a year.
Jamie......
|