Up to how much more fuel will you use by driving at 70 mph, compared with driving at 50 mph?

Explanation: Your vehicle will use less fuel if you avoid heavy acceleration. The higher the engine revs, the more fuel you'll use. Using the same gear, and covering the same distance, a vehicle travelling at 70 mph will use up to 30% more fuel than it would at 50 mph. However, don't travel so slowly that you inconvenience or endanger other road users.

Category: Safety and your vehicle

References: The Official DVSA Guide to Driving: Section 17