At what speed do cars get optimum gas mileage???

Answer 1

It is around 40 mph. The engine is actually more efficient at 55 or so but the rolling resistance and wind resisitance goes up fast with increased speed.

Answer 2

Well, this depends on a number of variables, and can change greatly from car to car, even of the same model and brand.

On a gasoline-powered, non-boosted (not supercharged or turbocharged) vehicle, the easiest way to find the optimum cruising rate for highway driving is to find the speed at which the engine makes the greatest amount of manifold vacuum. The greater the vacuum, the greater the gas mileage. This check must be performed while driving, preferably on a long level highway, as going uphill will make the engine work harder decreasing manifold vacuum. The opposite is also true (downhill=less work=more vacuum.)

My 1969 F-100's optimum cruising speed is between 60-65 MPH, and my 78 Pinto's optimum cruising speed is around 75MPH. I can get upwards of 28mpg in that little Pinto, and almost 16 in the pickup.

Answer 3

Sitting still with the engine shut off!! A serious answer to this question would have to depend on what kind of car, what engine it has, what the gear ratio is, and several other variables. Best bet is to ask the dealer about your specific car. In general, a constant speed somewhere in the 40 to 50 mile an hour range is USUALLY best for mileage.

Answer 4

actually the RPM's the motor can run at before it stalls the engine.

For example. I owned a 1995 Geo metro 3 cylinder. I drove around town in 5th gear to save gas. The rpm's were very low and I had to down shift to climb hills etc etc. But I saved butt loads of gas. If you have an automatic transmission then the transmission knows. With an over drive tranny I would say 45mph when the over drive kicks in. with a 3 speed tranny then 40mph.

The old saying the faster you go the more you save is false. Wind speed variations, more fuel consumption when your past your transmissions optimal point.

Answer 5

i own a repair shop,and they did a test to see where most cars actually got the best mileage at,and they found that most average cars got better mileage at 65 miles per hour that's why the speed limit did go back up on certain free ways,on an average it takes less gas to keep one at 58-65 miles per hour than at trying to keep it at 55 especially with today's cars,they are designed to run more efficient ,that's why we have the transmissions that have 5 and 6 speeds in them now,there more efficient to operate than the older 4 speed and 5 speed transmissions was,,every car i own will do better at 65 than at 55,i have averaged them out before,and i do better but you cant always drive 65,but they will be more efficient at the rate of speed,good luck i hope this helps.

Answer 6

The speed at which your vehicle obtains the best possible
mileage will be (passenger car) when the engine is operating
in the middle of it"s power curve.... most cars this will be in the
area of 1800 to 2200 RPM Range.. just a rule of thumb though and does not apply to every vehicle.

Answer 7

0 mph

Answer 8

About 55 mph.

Answer 9

under 2000 RPM and under 60 MPH

Answer 10

the speed limit