Can you save gas by driving fast?

Question

Q1: I am driving 40 miles an hour and in 1 hour i would have driven 40 miles.

Q2: I am driving 80 miles an hour and in 30 min i would have driven 40 miles.

My Question is that if I was driving 40 miles my car would be driking gas for an hour. but if I drove my car for 30 min at high speed my car would only use gas for 30 min. (even though I was driving faster than 40 mph I only wasted 30 min of gas doesnt it equal out to be the same no matter how fast or slow u drive?

Answer 1

You forgot to consider the increased consumption rate of that gas needed to sustain a speed of 80 miles/hr. In other words, you would use less gas driving 40 mph for 2 hours than you would to drive 80 mph for 1 hour.

Answer 2

No way. Aerodynamic drag slaughters you at 80 mph.  You can't make it up in gearing.  40mph wins by a WIDE margin.  It's very close to the "sweet spot" for automobiles, the point where the driveline is most efficient yet aerodynamic drag hasn't started hurting bad yet.

I once did some MPG experiments on my little car.  At 50-55 mph I got 50 MPG.   At 80 mph (desolate rural interstates in Nevada-Wyoming) I got 32-35 MPG, and I had altitude in my favor.  (thin air = less aerodynamic drag.)

I did the same in a 305 Suburban.  (yes they once put 305s in em.)  @50-55 mph = 20 MPG.  @70 mph, more like 15 mpg :(

But hey.  Do some experiments of your own. Burn a few tankfuls at different speeds and see whatcha get.

Answer 3

You burn more gas per hour at 80mph because you have increased drag. The amount of energy required is a function of distance and not of time (though I'm sure engine efficiency would be a problem at very low speeds).

Answer 4

It depends on a lot of factors.  If you have a very aerodynamic car then the increased wind resistance at 80mph might be overcome by such things as axle gearing, transmission gear, engine, etc.

Point 1:  At 40mph a lot of cars will be in 2nd or 3rd gear but in a car like a Camaro with a 6spd. manual transmission it would be in 6th gear (double overdrive) and it would be very likely that the engine was actually turning slower than at 40mph.

Point 2:   All engines also have powerbands which is the rpm range where the engine will burn fuel most efficiently.  If an engine is out of its powerband at 40mph but operating at peak efficiency at 80mph then it may be making a lot more power with the same amount of fuel consumption.

Cars are designed to operate at certain speeds.  The typical sedan might be calibrated so it gets its best fuel mileage at 55-70mph.  But a performance car might be calibrated to get its best mpg at higher speeds.

From Wiki:  The choice of car and how it is driven drastically affects the fuel economy. A top fuel dragster can consume 6 U.S. gallons (23 L) of gasoline (petrol) for a quarter-mile (400 metre) run in about 4.5 seconds, which comes out to 24 gallons per mile (5600 L per 100 km).  

Ok, so I just thought that was interesting!  Typically the slower you go the better mileage unless the car is designed otherwise...but possible...yes.

Answer 5

I think driving faster actually uses more gas!

Answer 6

A car engine has a speed at which it is most efficient round the point of maximum torque. Over 60 mph however wind resistance increases the fuel consumption . Most cars do best about 50mph.. It is acceleration that wastes the gas.

Answer 7

The faster your motor goes, the more gas it drinks.

Also, the faster your car is moving along, the more air pressure is pushing against the front of your car requiring more fuel to overcome the force.

You can try to break through the shock wave of the sound barrier to drive faster, easier, but I have found that where I live, the traffic lights are just a little too close to get up to the right speed.

Best Wishes

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Answer 8

Driving slower saves gas.