Does the trip computer on my car give accurate fuel economy readings?

My Ford Mondeo the dashboard info tells me my average mpg is 57.2 - way above what I see on Real MPG. Could this be a true figure or computer error?

Asked on 15 November 2018 by Jim Livingstone

Answered by Honest John
Just a standard error. The computer does not actually meter the fuel, it only 'estimates' the economy. Try a couple of consecutive brim to brim fills to calculate what it is really doing.
Similar questions
Do you have a top 10 or similar of most economical cars? It would be nice to see a list that would have specific engines included, i.e. Ford Focus 1.5 diesel.
Can I reject a used car if the fuel economy is very different from what I was told?
Why do summer and winter mpg figures vary?

Value my car