Does driving at faster speed use more gas?

Yes it does. That’s why they rolled back the speed limit to 55 in the 70s. Generally speaking, the lower your tachometer (tells you your RPMs), the lower your gas useage.

Driving at higher speeds uses up way more gas.

yes driving faster burns more gas,because your engine rpm is faster so it would have to be using more gas.but you really new that right.

Yes. Every 10mph above 55mph uses another gallon/hour, I believe. Faster driving means engine is burning more fuel to produce more power. Unless you’re driving downhill both ways (and neutral drops are not a good thing for your driveshaft, BTW)

driveing fast uses more gas. On the other hand though highway driving uses less gas than city driving due to stop and go traffic in the city.

Depends on the car and on the speed. Going slow, especially if in stop and go traffic/city driving, will cause the worst fuel economy. Typically vehicles are actually most efficient when cruising somewhere between 50-80. For my car, 95 BMW, I reach best fuel economy at around 73mph. If you go beyond 80mph, however, you will be burning extra fuel not only because of higher RPM’s but also because you will be working against increased aerodynamic drag.

Be sure to keep proper tire air pressures, use the recommended fuel grade, and keep your car maintained properly to boost fuel economy even further.

That depends upon your cars drag coefficient (aerodynamics), and the gear ratio for the final drive, and ratios for the transmission. My car has a really tall road gear (I can do 55 mph in first gear). The aerodynamics makes this car very efficient at gliding under the air. It has a downward sloped hood, with retractable headlamps, so daytime driving has less drag, than at night. The engine and transmission have both been tuned to give maximum power on demand, while maintaining great MPG when just cruising down the freeway.

For the most part, engine revs do not matter, since the computer is looking at what it is you are trying to do. If you are just smoothly going down the highway at 70 MPH, with the cruise control on, the computer sees that, and adjusts the engine and transmission for maximum efficiency. If you are shotgunning the gas pedal all the time, the computer sees that, and adjusts for that sort of driving, resulting in fewer MPG. At 55 MPH, the tachometer shows me about 2000 RPM, at 70 MPH it shows me about 2500 RPM, that’s just not much difference in the revs per mile.

The main goal of the computer is to try to stay at a 14:1 air fuel mixture (lower emissions), if you are driving sensibly, the computer can achieve that goal more often making no difference in how fast you go.

I own a 1991 Chrysler LeBaron Premium LX w/3.0L V6, and 4 speed automatic transmission. Sequential port fuel injection, and all well maintained (the key for longevity, and efficiency). This old car looks great, and drives even better. It gets between 27~30 MPG depending on how I am driving. Highway miles are with the cruise control set usually at 70 MPH. I have tried to see if it will do better at 55 MPH, or 65 MPH. I noticed better MPG at 70. This car has a good drag coefficient anyway, so the faster it goes, the better the air flows over the body.

Yes – the higher the RPMs- the harder the motor is working/using more gas. Thats why most cars have an overdrive, to reduce the RPMs. Needless to say, going faster might get you home /work in little as 5-6 minutes faster.
Ways for better milage:
Tire air pressure – make sure are properly inflated
Tune up- new plugs, airfilter, fuelfilter, oxygen sensor, change tranny fluid/filter – should help on milage
Driving with windows up
Pickups: driving with tailgate down doesnt help milage, actually worsens it.
Extra unecessary weight makes milage suffer( large stereos, extra weight in winter, ect)

I’ll make it short and sweet. Doubling your speed requires four times the horsepower to move the car. The rest is obvious.