Dealing with a disparity in mpg figures

HELPDESK: Motoring editor MICHAEL McALEER answering your motoring queries

HELPDESK:Motoring editor MICHAEL McALEERanswering your motoring queries

From JF Campbell: Last autumn I traded in my 2007 Skoda Octavia Ambiente 1.4 petrol for a similar model, the main difference being that the new car has dual zone air conditioning. I have never owned a car with air conditioning before.

For some years now I have kept regular weekly mpg records. Apart altogether from my records and, without any change in motoring pattern, I became aware within the first three weeks that my mpg was noticeably down. I contacted the garage and they told me that this was because of the air conditioning, although they did take the car in for what they called a diagnostic check. Nothing showed up as a result, which to them appeared to confirm their initial assumption.

My city driving has gone from 33.6mpg to 27.7mpg and long distance driving from 46.8mpg to 37.7mpg. I don’t understand the link between air conditioning and fuel consumption. Had I known in advance that it would have such an effect, I’m sure I would not have opted for it.

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We spoke with Skoda Ireland’s managing director Colin Sheridan and he said there are many reasons fuel economy figures may differ between the cars, one of the most likely being that the car needs to be run-in. He said that he would normally expect cars to record single-digit percentage increases on official figures due to the air conditioning system. He was surprised by the difference you have recorded and says it requires further investigation. Skoda will contact you directly about the issue, but there’s no doubt air conditioning does draw some power from the engine.

The problem with official figures is that the standard test is carried out with such devices switched off. While these figures provide useful comparisons between models in an “all things being equal” scenario, they often bear little relationship with the real world.

In the US, consumers were so disgruntled by the failure to meet published fuel economy figures that the Environmental Protection Agency (EPA) added an additional grading system from September 2008. Cars now carry an EPA label that lists realistic annual fuel costs based on a given number of miles; figures for the sort of mpg most drivers can expect on city and highway driving; and where this range falls in comparison to vehicles in its class. It would seem a sensible addition to the system.

From KC: I know you don’t usually cover vans, but I have just opened a small florist and need a delivery van. I want new in case there are any problems that can be covered by warranty. I have a budget of about €12,000.

If the budget is ex-VAT, you have plenty of choice. There are many car-derived vans on the market, taken from smart superminis like the Opel Corsa or Mitsubishi Colt. We contacted Gerry Murphy of Fleet Transportmagazine, who suggests the Fiat Fiorino. It can be purchased for €10,504 ex-VAT. It's more spacious than others but not unwieldy and comes in a range of loud colours that will attract attention to the shop.