Is the trip meter as inaccurate as the speedometer?

I filled up today and started to calculate my mpg using the trip meter reading, when it occurred to me that it is probably as inaccurate as the speedometer itself (in my case about 7-8per cent optimistic). Or are the mileage readings on the odometer and tripmeter more accurate, assuming tyre radii are standard?

Asked on 11 May 2013 by TW, via email

Answered by Honest John

I do a regular journey, exactly the same distance, in different test cars and the mileage readings have varied between 294 miles and 312 miles. Mazdas give the lowest readings.

Tags: fuel economy trip computers speedometer

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