How can I calculate the true mpg in my Mazda 6?

I recently bought a 1.8-litre petrol Mazda 6. The ‘info’ button reveals I am achieving between 42 and 43 miles per gallon. How accurate are these in-car gizmos at calculating miles per gallon?

Asked on 24 March 2012 by GM, Heswall

Answered by Honest John

Not very. You can check by filling up to the brim, writing the mileage on the ticket, then filling up to the brim again after 300 miles or so and writing that mileage on the ticket. Multiply the litres on the second ticket by 0.22 to get gallons, subtract the first mileage from the second mileage then divide the result by the gallons. Of course you then need to allow for odometer inaccuracy, but Mazdas are generally very close to accurate.

Tags: fuel economy real mpg

Similar questions

Why is my Mazda 6 returning just 40mpg when it is advertised as returning up to 52mpg?

I bought a Mazda 6 estate 'Takuya' edition in September 2010. It’s a 2.2TDi (163ps) with an advertised mpg of 40.9 urban and 52.3 combined. Given the rising price of fuel, the mpg performance was a key...

Do the 'economy' tyre pressure settings on my Vauxhall Insignia help with mpg and will they affect tyre wear?

I recently bought a secondhand 2009 Insignia 2.0 CDTI SE to replace my 2001 Toyota Avensis 1.8 VVTI. I hoped to improve fuel economy with my change in car. The Insignia, which is a diesel, has only just...