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post #2 of (permalink) Old 11th April 2007
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Hi there JordyLad, and welcome to the forums.

Good question - the classic 56mph figure was just a benchmark used in the government road testing, and for comparative purposes only.

The most 'efficient' speed will vary from car to car, and even for engine/transmission type, but a general rule of thumb method is;
  • look up your owner's handbook and locate the power characteristics for your specific car.
  • find the maximum torque figure, and what rpm it is developed.
  • if your engine is at that rpm 'sweet spot' in any gear - you are at the most fuel efficient mode that the car has.
The reasoning is simple, use too many revs - then the fuel is being burnt more rapidly than is necessary, change up too early, and you will be forever changing down to maintain progress (remember, every time you change gear, the engine is still using fuel). At the max torque engine speed, you shouldn't have to change down (unless you encounter an obstruction).

Hope that helps, try it out and see how you fare.

Best wishes,


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