Does it really help your gas-mileage to drive slower?

Question

I keep reading/hearing that to save gas you should drive slower.

I regularly drive much faster than the posted limit. 70mph here in MI (sssshhhh, don't tell anyone). I can't abide going any slower than that honestly!

Optimally 55mph will give you the best gas mileage. I find this speed ridiculous! Does anyone ever drive on the freeway this slow? If you have did you notice any gas savings?

Answer 1

Every vehicle is different.   RPM's matter.  

The higher RPMs ..the more gas you use.

Drive your vehicle at the lowest RPMs...better gas mileage.

If you have a standard trans...downshifting eats fuel.

Drive smart!

Answer 2

Power to overcome wind resistance is a squared function, there the wind drag at 80 mph is 4 times as great as at 40 mph.  No matter what car you are driving.

on a recent trip, over a 1000 miles long, on the way there I ran approximately 70mph and got 18.4 mpg.

on the way back where I played escort to a large over sized load who could not do about 53 mph, same pickup got 26.7 mpg.

Answer 3

Oh yeah...I went from 70+ to the speed limit (65mph) several months ago.  My mpg went from 22 to 27.5 on average.

I go the limit ever since, using cruise control as appropriate, and I can tell you that my gas card bill is 15-20% less each month.

Oh, important:  RIGHT LANE, PEOPLE!!!

Answer 4

It's your money... Spend it any way you like, but you will be putting less money in the pockets of the Arabs if you keep your speed down.

Answer 5

LOL I hear you. I usually do 80km/h (about 55mph) on the wider city streets (which is about 70km/h), and much faster on the highway (a little under 140km/h). I'm all for the environment, but i don't have the patience or the attention span to drive 80km/h constantly.

Answer 6

Yes, fuel economy is dependent on speed.  You will definitely save gas if you drive slower.  Any engineer will tell you that.  

Whether you want to or not is up to you.

Answer 7

the speed limit on the highway near me is 70mph. I find if i go above 75 my gas mileage goes down.