Best Speed for Gas Milage

Power/Fuel
1

I think Tom and ray said the 65 MLH was the most efficient spead for a car to travel? Would this be for all makes & models? I have an Impala without a tachometer to watch the RPM’s. On the highway, is auto cruise efficiency that much different than driving w/o cruise?

2

A lengthy discussion on the relationship between mileage speed has already been undertaken here: http://community.cartalk.com/posts/list/140809.page

3

The answer to that one is no where close to that simple. Follow the link above.

4

55 to 60 mph in overdrive is where you should be for that scenario.

However, the way people drive today, you’ll likely get run over during a fit of road rage.

5

Depends what you drive and how you drive it and you will have to experiment. If you have a big van with a 4.6 engine, it might not make much difference if you stay near the speed limit.

6

too bad your car doesn’t have a tachometer.

i have found that while speed is a significant factor in mileage, and that generally it’s always best to be in as high a gear as possible, keeping the RPMs moderate to low is the single BIGGEST factor.

i actually get BETTER mileage in low speed (35 - ~52 mph) suburban/urban driving than i do on trips. largely because in the former, i can always keep my rpms at 2300 and below. even as low as 1500 rpm.

unless i stay at 55 mph, my rpms on trips are always HIGHER, for LONGER periods. hence, the engine is ALWAYS turning faster, burning more gas.

7

Though not directly related to the question:

Back during the gas shortage of the mid-70s, there was a big competition to see who could get the most mileage out of a gallon of gas. Big oil and car companies participated. The vehicles they built were very small “go-cart” type vehicles.

  • The winner got around 1600 miles per gallon.
  • The average speed they all traveled at was about 12-14 miles/hour.
  • The competitors that built farings for the front of their vehicles got about 200 more miles per gallon than those who didn’t.

Joe

8

You need to be in the highest gear and operate the engine at high enough RPMs that the engine does not lug. For an Impala with a 4-spd automatic, 55 MPH should be fine. I would, and do, drive 65 or 70 MPH if that is the speed limit. I even drive 55 if that is the legal limit. I get about 28 MPG in rush hour traffic in a similar car.