It’s important to take into consideration the type of fuel your car will use in order to work out the running costs.
Diesel or petrol?
- Diesel cars tend to use less fuel than petrol vehicles and do more miles to the gallon (mpg) or litre when doing long distance or motorway driving. However, diesel cars may be more expensive than petrol, and generally have a higher Advance Payment.
- Engines powered by diesel generally emit less CO2, but they do produce more air quality pollutants than petrol engines. However, to counteract these effects, many diesel cars have Diesel Particulate Filters to remove sooty particles from the exhaust gases of vehicles.
There are advantages and disadvantages to both diesel and petrol cars so it is important to choose the right vehicle for you. Generally speaking, if you mainly drive long distances or on motorways, then a diesel engine might be good for you. On the other hand, if you spend more time in town doing short journeys at lower speeds, you might be better off with a petrol engine.
A word about miles per gallon (mpg)
You can find out the average annual miles per gallon (mpg) of all vehicles on the Motability Scheme by using the Car Search . The mpg figure will help you to decide how economical a car may be in terms of fuel consumption. However, it’s worth noting that fuel consumption figures should be used for comparison purposes only as they may not be the same as the figure actually achieved. This is because of the way they are calculated.
How are official mpg figures calculated?
There have been various standardised tests to calculate the miles per gallon (mpg) figure for each car over the years. The current method (monitored by the Department of Transport) sees cars being tested in a laboratory.
The car is fixed on a set of rollers known as a rolling road, and a series of drills including braking and accelerating are performed; these are designed to replicate types of driving.
The exhaust gases released are measured using special equipment. From this, the emissions ratings are calculated as well as the fuel economy (mpg figure).
This test involves two parts:
The Urban Cycle
This begins with a cold engine start; the car is stopped and started a number of times to replicate town driving. The maximum speed is 30mph and the journey lasts two and a half miles.
The Extra Urban Cycle
This lasts for 4.3 miles at speeds of up to 75mpg designed to replicate out-of-town driving.
The results are used by car manufacturers. You will also see a mph figure for each model on the Car Search.
The effect of these tests
The tests are designed to provide standardised and comparable results which can be repeated for every car.
Because they are carried out in a lab, they may not cover the huge range of variables which affect the fuel economy in real-world driving conditions, including different driving styles, travel habits (for example if you regularly drive on a motorway), things like extra weight from passengers, luggage or optional extras fitted to the car and so on.
There are calls to reform the way these figures are calculated. The transport minister Norman Baker admitted there were “limitations to the current test” and that improvements were planned. However, he also added that until European countries agree on a better approach, the existing test was still useful.
Until such change takes place, it is best to treat these figures for comparison purposes only; the actual mpg figures a car achieves will vary because of the above factors.
There may be ways you could improve your mpg. Why not make a few changes to the way you drive by trying these environmentally-friendly suggestions.