Measuring Fuel Efficiency: 9 Things That Have An Effect

Measuring Fuel Efficiency: 9 Things That Have An Effect

Last updated on September 5th, 2023 at 12:00 pm

The choices you make as a driver can save you fuel and reduce wear and tear on your vehicle.

No matter your end goals, the actions you take as a driver can lead to a lower risk of accidents and lower repair bills.

When measuring how fuel efficient your vehicle is, consider the following items and use the tips below to get the most out of the fuel you burn.

  1. Driving habits
  2. Vehicle maintenance
  3. Gasoline grade
  4. Tire pressure
  5. Air conditioning
  6. Vehicle weight
  7. Automatic vs manual transmission
  8. Weather
  9. Driving speed

car fuel economy rating information sheet

1) Driving habits

Putting the pedal to the metal will cost you. Rapid starts and quick stops burn more fuel and will require you to get your brakes serviced more often.

While coasting is not terribly exciting, it can save you both fuel and repair costs.

If you drive an automatic transmission, it’s easy to punch the gas pedal when you take off from a dead stop. Instead, accelerate slowly.

When you see a stop coming up, take your foot off the gas and let inertia slow the vehicle down.

Apply the brakes in a timely fashion, but let the speed of the car drop naturally before you press on that pedal.

Poor driving habits will result in poor fuel efficiency.

2) Vehicle maintenance

A poorly maintained vehicle has to work harder than one that is in good repair. If your

  • air filter is dirty, your engine will run hotter
  • oil and filter are dirty, your engine will enjoy less protection from wear and tear
  • radiator fluid is low, your engine will run hotter and have to work harder

If you live in a part of the country that includes large temperature swings, get your oil changed by the calendar and not by the miles.

Using the wrong weight of oil in cold country can leave your engine chugging along with metal-to-metal pressure instead of full lubrication.

Additionally, if you need to park your vehicle outside in cold country, it may be a good idea to use a block heater.

Count on a poorly maintained vehicle to provide you with poor fuel economy.

3) Gasoline grade

Review your manual to see what grade of gasoline is best for your vehicle. Every manufacturer is different and manufacturers may have different requirements for different engines.

For example, if you drive a sports car, it will need a higher octane fuel for optimum efficiency. If you drive a minivan or a standard pickup, the engine may be able to tolerate a lower octane.

Octane refers to the ignitability of the fuel you put in your car. While gasoline will always ignite, a higher-octane fuel will ignite with less compression.

There is a great deal of pressure inside your gasoline engine and if you use a fuel that will not ignite under compression, the engine will knock.

Because sports car engines are designed to be both lightweight, to reduce drag, and powerful, for greater speed, the octane rating you choose can make your engine run very rough.

So does higher octane gasoline improve fuel performance? Not always but it certainly can. According to, for most vehicles, higher octane fuel will result in improved fuel economy.

Although it doesn’t make a huge difference in many cases.

For several reasons, It’s worth it to pay the extra and put the right fuel in your car.

4) Tire pressure

Under-inflated tires leave more tire on the road as you drive. This “slap” may not be visible or noticeable by the driver, but your car will have to work harder to overcome the drag caused by low tire pressure.

Under-inflated tires can also be damaged over time if you continue to drive on them. The sidewall of the tire can be weakened if you drive on a low tire. Check your tire pressure on a monthly basis.

Over-inflating your tires will not improve your fuel efficiency. In fact, over-inflated tires can be quite dangerous.

When your vehicle is bouncing around on over-inflated tires, you are not in contact with the road or in control of the car.

Both under-inflated and over-inflated tires will result in reduced fuel economy.

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Check your manual and review the posting on the inside of the driver’s door and inflate to the correct pressure for your vehicle and tires.

The correct tire pressure can result in a 0.6%-3% increase in fuel economy when compared to improperly inflated tires.

under inflated car tire

5) Air conditioning

Running your AC may be necessary in hot climates, but it will take a lot of power to keep the car moving and the AC cool. There are steps you can take to keep your vehicle cool without running the AC full time.

Use sunshades to keep the inside of the car from warming up. If possible, use an exterior sunshade to keep heat out of the vehicle entirely, or tint the windows.

Make sure to leave a window cracked to reduce the amount of heat build-up over the course of a day.

Your AC compressor runs when your defroster is on; even if it’s blowing hot air, it’s pulling moisture out of the air in the car and keeping the windows clear.

Use the defroster for as long as necessary, and if you need more heat in the car, switch to your front or floor vents.

Using your vehicle’s air conditioning will increase fuel consumption by about 20%-25%. Air conditioning will cause more fuel burn than any other auxiliary feature that your vehicle has.

6) Vehicle weight

The heavier your vehicle, the harder your engine has to work to move it around, and the more gas you will burn. Carrying around extra weight can also be hard on your

  • suspension and shock absorbers
  • brakes and stopping distance
  • handling and tires over time

If you need to haul bikes, tools, groceries, or camping supplies, do so. When your trip is over, unload the car.

Leaving your car under an extra load of unnecessary stuff for an extended time wastes more than gas.

In most cases, a heavier vehicle will be less fuel efficient.

7) Automatic vs manual transmission

The faster your RPMs climb, the more fuel you will burn. In an automatic, you’re stuck with the gears as assigned by the car.

If you’re driving a manual transmission on a flat surface, do your best to get through the gears quickly for the best fuel efficiency.

Do make sure not to shift your manual transmission too early, especially if you’re climbing a hill or carrying extra weight.

You can end up lugging the engine, which can lead to a great deal of heat build-up in the cylinders.

If you’re driving a vehicle that is under load, higher RPMs are better than overheating.

In many cases, a vehicle with a manual transmission will provide better fuel economy than a vehicle with an automatic transmission.

manual transmission car shifter

8) Weather

As noted above, running your AC while driving will increase your fuel consumption. To get the most out of your gas,

  • get your driving done early in the day to avoid having to use AC
  • keep heat out of the car with shades and tinting
  • avoid using your defroster by parking your car with the big windows to the south or east
  • If the sun can clear your windshield, you can get on the road without having to run the defroster

For those who deal with ice and snow, simply driving during daylight can do a lot to keep your fuel consumption down.

If other drivers get out and create a path, you can avoid having to churn through the snow. Driving in snow or poorly maintained roads will have a negative effect on fuel economy.

According to, driving in cold weather can significantly reduce your vehicle’s fuel economy by 15% with an outside temperature of 20 degrees F compared to 77 degrees F.

9) Driving speed

Check your manual for the recommended and most efficient driving speed. The newer a car is, the more the design has been impacted by CAFE standards, or corporate average fuel economy standards.

Running your vehicle at the optimum speed on the highway is a great way to avoid burning too much fuel, especially if you use cruise control.

At higher speeds, your vehicle will be subject to higher drag (tire rolling resistance and air resistance).

At speeds above 50 MPH, the reduction in fuel economy becomes more apparent.

If you notice your fuel efficiency dropping over time, check your tires and consider emptying the vehicle of unnecessary gear.

speedometer showing 200 mph

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