The MPG on my car is terrible - what could be the cause?

I have a Vauxhall Insignia and all seems mechanically sound with 68000 miles on the clock, a recent service and full service history plus new discs brakes all round. When I bought it I was getting around 19MPG for short city journeys we rarely use it for motorway driving but on the occasion we did it went up to around 31MPG but has since gone down to around 10 MPG for short city driving.

Asked on 3 June 2024 by KYE REAVILL

Answered by David Ross
If you are having concerns about increased fuel consumption we would suggest the starting point is to do your own fuel calculations to see how accurate the car's on-board computer is. Brim the fuel tank, reset the trip meter and fuel consumption display then carry out a regular journey. Once completed, brim the tank again and note the mileage covered and you can then calculate accurate MPG and compare this to the car's display.

Assuming the fuel consumption is still higher than normal, it would be worth checking the car over for any potential causes. Incorrect tyre pressures, any unnecessary weight in the cabin or boot and increased use of air conditioning can all affect fuel consumption, or it could be a fault with the vehicle is causing increased consumption. If the new brakes are binding even slightly this could have a significant affect on fuel economy, but beyond this you may need to have the car inspected by a garage to look for any other causes.
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