October 10, 2011
Which saves more fuel, driving faster or driving slower or is there an optimum?
Given a relatively open road, equal distance, same driving skill etc.
I have heard conflicting advice from people, some saying faster, others slower. Some say it differs on fuel type such as diesel being better slower and petrol vice versa.
I used to believe in the ‘faster theory’ (via intuition) but I’m now conficted.
NB: ignore accidents or safety or being late.
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Filed under Gas Conservation FAQ by on Oct 10th, 2011. Comment. 
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Comments on Which saves more fuel, driving faster or driving slower or is there an optimum?
Medium, usually. Does your car have a tachometer? Watch that for a sense of lowest RPM’s per mile, most cars it will be about 60 mph (100kph). More important is to get to your cruising speed and maintain it without fluctuation. use cruise control if possible.
I tried driving slower and taking off easier and I saved gas. Did it for a week
on cars and trucks all things are made for optimum turning/usually american and jap cars are about 60 -65/you can feel the car just settle in and cruise real easy/beemers are much higher 70+/these settings are the easiest for the engine and the most effecient running/can fell the car just slip in easy try your car at about those speeds
It depends on the gearing, the frontal are of the vehicle, aerodymic coeeficient……. I’ve never had a pick-up get better than 17………My Mustang gets 17-18 at 75-80 MPH at 2,000 RPM with a 5.0L and 3.55 rear gears and a .59 overdrive in the trans. By contrast, my Lincoln LS has a “sweet spot” at about 2,600 to 2,800 (80-85 MPH) it’s 3.9L with a 3.31 rear axle and an overdrive in the 5-speed automatic…. it will get 27-28 MPG in this “cruise missile” mode. This car is a “tourer” much like the Beemer example the other answerer noted.
Most North American cars are tuned and geared to produce optimum fuel mileage at approx. 55 MPH.
There is an optimum speed at which fuel economy is best.
Take a look at the graph here http://www.best-money-saving-tips.com/fueleconomy.html
You can see that maximum MPG is around 55 MPH.
Drive faster and you get too much air drag. Drive slower and you waste fuel on keeping the engine running.
The optimum speed is unique for each car and depends on many variables such as engine size and make, car weight, car shape and much more.
Most cars, however are designed foe maximum fueleconomy at the legal driving speed, around 55 MPH.