“Be careful not to over-rev the engine, as this will use more fuel, and make sure you don’t labour the engine by being in a gear that’s too low for the speed and terrain.
“Generally, petrol cars are at their most economical between 1500 and 2500 rpm, so you should aim to change up to the next gear whenever you exceed the higher end of that band.
“For diesels, it’s between 1300 and 2000 rpm.”
When the RAC completed its “Record Road Trip” in an Audi A6 ultra, it found that the car’s optimum fuel economy speed was 52mph in seventh gear on the flat.
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