Does freewheeling improve fuel consumption?
Believe it or not, but the answer is “no”.
Here is a very simple explanation
- An idling car needs fuel to be sprayed into the combustion chamber by the injectors to keep the car running or else the engine will die.
- In contrast a vehicle in motion and in gear, without any accelerator inputs is running against the compression of the engine and thus need no fuel injected to keep the engine running.
- Therefore a vehicle driven in a high gear down a hill with no accelerator inputs will actually consume less fuel than a vehicle freewheeling.
We recently put this theory to the test
- Our test vehicle was an Audi A1 1.2T FSI
- Our road section was the same 2.5Km downhill section of road.
- We drove at roughly the same speed, although the average in neutral gear freewheeling was actually a bit lower than our in-gear average speed we achieved.
- Herewith our results as per GPS unit and the vehicle’s on-board trip computer:
Freewheeling Fuel Consumption Test Results
||In top gear with no or very little throttle inputs
|Time taken to complete section
||2-minutes and 25 seconds
||2-minutes and 4 seconds
|Fuel Used as per vehicle’s trip computer
||1.4-Litres per 100Km
||0.9-Litres per 100Km