At what speed should you drive for best fuel economy?

Question

At what speed should i drive to get the best fuel economy possible

engines is a 4 cylinder

Answer 1

This varies for all engines even within their own cylinder range. There are two ways to determine this: the first to determine your car's highway mpg, which is usually set around 55mph.  The second is to observe the generic mpg range scale.

For some reason I seem to be unable to load the best sources of the two, but here is where I go to figure this info out:

www.fueleconomy.gov

They have a section devoted entirely to improving your own fuel economy. You can also find this info at the EPA gov and forbe's mag. has the best tips in my opinion.

Keep in mind that sometimes it's better to avoid rapid acceleration to maintain this speed. You will not only burn more fuel, but you may also have to stop sooner and idol longer, plus you reduce your high speed duration.

Answer 2

55-65 mph i heard from my history teacher.

Answer 3

At whatever the minimum speed you can get the torque conertor to lock-up (auto tranny). This is usually between 40-55mph.

When the TC locks, you are getting better economy

Answer 4

Experimentation is your friend.  Know how to measure your MPG from tank to tank, and drive a few tankfuls at different speeds.   My experiments yielded:

50-55 MPH -->> 49.9 MPG @ sea level

65-70 MPH -->> 39.5 MPG @ sea level

75-80 MPH -->> 35 MPG @ high altitude and lower octane.

High altitude gives better MPG because of less air resistance.  At 80 mph, almost all your drag is air resistance.

Here's what you're up against.  

- A car has some energy burn that is constant, no matter what the speed - for instance lights, wipers, computer controls, A/C.  For that, the faster you go, the less time you run those loads per mile, so faster=better.

-  You have losses spinning the engine, and your engine spins slower in higher gears, but to be in top gear you have to be going over 40-45.

- You also have rolling resistance - which is fairly proportional to speed, twice the speed twice the rolling resistance.  Doesn't make much of a difference to MPG.

-  And then there's aerodynamic drag, which is a very exponential curve -- it's nothing at 20 mph and absolutely enormous at high speed.   This is why faster stops being better.

My guess is on most cars that happens around 45-50 mph.

A/C is tricky.  It's a constant load, so the faster you go, the less time you spend going a mile, the less A/C load you have for that mile.  Still it's very wasteful - if you care about fuel economy, shut it off.   At high speed, windows down makes lots of aerodynamic drag (thus the loud noise) -- so at freeway speed, ideal is A/C off, windows down, fan on.  The fan takes very little energy.

How do you measure fuel economy from tank to tank?  Easy - fill up your tank each time until it clicks once (easier with credit card pay), and compare the gallons pumped to the miles driven since last fillup. If you have a trip odometer, that's cake.  Divide miles by gallons = MPG.  Average over 2 or more tanks for best numbers.

Answer 5

my drivers ed teacher says once you go above 60, it uses much more gas

Answer 6

the best bet is to just drive the speed limit!!!!!! And sloooow if ur in a side empty street. Basically tahst it. or walk when u can  , u don't need to drive for EVERYTHINg.

Answer 7

About 45 mph, after that wind gets to be a problem.

Answer 8

I drive around 45-55 on the streets but what helps is when you take off from a stop, i just giv a little gas and take my time to get to the speed i want

Answer 9

The speed limit. However, you will have a lot of tailgaters on your tail.

Answer 10

For most cars - the "sweet spot" on the speedometer is in the range of 40-60 mph. Smaller, lighter, more aerodynamic cars will get their best mileage at higher speeds. Bigger, heavier, less aerodynamic vehicles will get their best mileage at lower speeds.