Tyres

Tire fuel efficiency-economy and Fuel efficient, low rolling resistance tires

There are many factors that impact fuel economy (distance traveled per unit of fuel; miles per gallon - mpg), besides tires. One of the most important factors is a driver's behavior. Drivers that accelerate and brake aggressively or are frequently in the "stop & go" city traffic routine, will use up a lot more fuel than drivers that accelerate and brake gently and driving mainly in non-urban conditions. It's said that good driving habits can improve the fuel efficiency and could save you as much as 10% in fuel costs.

When comes to a tire fuel efficiency we must talk about the tire rolling resistance first and hence the tire fuel efficiency rating.

tire fuel efficiency rating

A greater number for "fuel efficiency" means that a tire is more fuel efficient.



What is a tire rolling resistance?

Tires affect vehicle fuel economy or efficiency primarily through the rolling resistance.

Simply put, the tire rolling resistance measures how much energy a vehicle engine must put into making tires roll along the road i.e., the energy loss caused by the friction between the tires and the road. So, the more rolling resistance the tire has, more energy/fuel is required to keep the car moving, to overcomes the rolling resistance.

Tires with low rolling resistance, LRR tires, use tread design and new materials to minimize the amount of energy required to move the car.

A tire rolling under vehicle's weight causes that the tire undergoes recurring cycles of deformation and recovery thus, creating the rolling resistance and wasting energy/gasoline.

tire rolling resistance

This is the moment to say how It's important to keep in mind that your tires are the only material connecting your vehicle to the road. But this connection is based on a small patch("contact patch") of each tire, connected to the road at any time.

Due to the rolling resistance and cycling tire deformations, a mechanical energy, otherwise available to turn the wheels, is converted into heat and dissipated from the tire. More energy, i.e., more fuel/gas must be used up to replace this wasted energy.

Therefore, by choosing low rolling resistance tires which require less energy and are more fuel efficient, you will use less fuel/gas and save money.

Combinations of tire features like dimensions, design, materials, and construction will cause tires to differ in the rolling resistance(usually expressed through the tire fuel efficiency rating) as well as in many other attributes: traction, handling, noise, tread wear resistance, and appearance. Once the tires are placed into service, they must be properly maintained to perform as intended regarding to all tire’s attributes. Maintaining the tire proper inflation pressure is especially important because it directly influence the tire rolling resistance (read more below).

Tire shoppers consider many factors when buying tires: braking performance, wet-weather grip, how long they last, and price. But considering a tire’s rolling resistance can save you money at the gas station.

Many tire manufacturers display a fuel efficiency rating for their tire models.

EU tire efficiency label.

EU tire efficiency label

Tire pressure impact on fuel economy – the easiest way to improve a car fuel economy

Another important consideration for optimal fuel economy, regardless of the type of tire on your vehicle, is maintaining the correct tire pressure. Keeping your tires inflated to the recommended inflation level helps in saving fuel/money. The second benefit is reduced CO2 emissions.

Even a few PSI (approx., 1 Pound-force per square inch = 0.069 Bar) under the recommended pressure can impact fuel economy.

According to the U.S. Environmental Protection Agency, underinflated tires can reduce fuel economy by about .2% for every 1 psi below the recommended air pressure. The reason is the underinflated tires have more flex in the sidewall, which creates more heat hence, a wasted energy. So, if your tires are even 5 PSI (0.34 bar) underinflated, you are losing at least 1% in fuel economy.

This does not mean that higher inflation, above the recommendation, is a good idea. For example, an overinflated tire will wear faster in the center of the tire, have less traction and will negatively impact the ride comfort and handling of the vehicle. Always keep the tire pressure at the vehicle manufacturer's recommendation!

Fuel efficient tires can have an important impact on the car fuel economy

Fuel efficient tires, environmentally friendly (eco-friendly) tires, low rolling resistance tires (LRR tires); these are all names that describe the same thing: the tires designed to reduce energy loss thus, to increase a car fuel efficiency.

Simply put, the fuel-efficient tires require less energy to roll. This finally translates into less fuel/gas used.

How much gasoline/money will I save?

Did you know that tires account for up to 20% of your vehicle's fuel consumption in passenger cars but can be as much as 30 percent of fuel usage in large trucks. While low rolling resistance(LRR) tires may only reduce that by 2 to 3 percent compared to a standard tire that doesn't have low rolling resistance features, it's still fuel savings – not only helping the environment(lower your CO2 emissions), but your wallet, as well, giving you more miles from your tank.

credit:Toyota RAV4 Hybrid2.5 VVT-i 2016 by Kickaffe, commons.wikimedia.org

toyota rav 4 hybrid 2.5 VVTi 2016

Using the current (2022.) average gas price of $4.84/gallon (regular; see gasprices.aaa.com), the typical driver of the one of the most popular domestic cars (e.g., crossover Toyota RAV 4) would save approx. $58 or more per year by using LRR tires.

For e.g., let's say your car gasoline economy is 31 miles per US gallon(mpg, or 13.18 km/l) and you cross 15.000 miles per year or 24.000 km. This is 483 gal/yr times 4.84 $/gal, equals 2337 $/yr. Savings could be 58 $/yr (2.5%). By choosing these types of tires(LRR) vs standard tires, over a five-year life span for a set of tires, this can easily add up to the equivalent value of getting one or two tires free. Not so bad? Remember, we are talking only about the tire rolling resistance. If you maintain proper tire pressure, change your driving habits, all of these could give you significant boost in the tire economy.

Tire manufacturers are cutting down on using materials harmful to the environment, while reducing friction, thus increasing fuel efficiency. As a result of less fuel used, CO2 emissions are also reduced, and the car becomes greener or "eco-friendly", with less wear on the tire, durability and longevity extended, which all lead to fewer tire shop visits.

Why choose a Low Rolling Resistance(LRR) tire?

Motivation for buying the LRR tires, besides aforementioned better fuel economy and savings, could be other benefits of this type of tires:

  • less CO2 emission;
  • reduced energy loss as tire rolls;
  • decreased required rolling effort thus, less stress on engine thus, longer engine life.

Other things which can impact the car fuel economy

Besides aforementioned factors that affect the car fuel economy: rolling resistance between the road and wheels, driving habits, correct tire pressure; there are:

  • overall car weight;
  • car speed;
  • efficiency of the heat engine;
  • frictional losses within the drivetrain;
  • rolling resistance within the wheels;
  • subsystems powered by the engine, such as air conditioning, engine cooling, and the alternator;
  • aerodynamic drag from moving through air;
  • energy converted by frictional brakes into waste heat, or losses from regenerative braking in hybrid vehicles;
  • fuel consumed while the engine is not providing power but still running, such as while idling.

A/T vs highway/street tires - Will All-Terrain tires increase your gas spendings?

You already know the importance of selecting the right tire for your vehicle, driving habits, road and weather conditions.

Tread type affects your gas mileage too. So, if you’re considering to buy a set of all-terrain tires(A/T tires), think about how they'll change how much you pay at the gas station.

car all terrain tires

All-terrain tires mean the tires designed for all-weather conditions and maybe some off-road driving. If your car takes you sometimes to the off-road path, then a simple highway tire isn't going to help you much. This is a reason why most tire manufacturers have started to make tires with low rolling resistance(LRR tires), including A/T tires.

The crucial difference between A/T tires and highway (or street) tires is that A/T tires are designed to grip to different types of surfaces, including off-road paths. Results are not so quiet ride and bad fuel economy. All-terrain tires tend to have shorter lives than highway/street tires, because of their treadwear. Highway tires are designed more for fuel efficiency, smooth rides, and longer tread life. The consensus is that on average, A/T tires decrease fuel economy by about 3% compared to their highway relative.

Not only do A/Ts adversely affect fuel mileage, but they also wear out faster than highway tires. So, if you’re not in need of A/Ts, you can stick with highway/street tires, and even find the ones that are most fuel efficient. The overall price of ownership is less for a highway tire. Switch to all-terrains if you plan on taking frequent trips off pavement or if aesthetics is more of a priority than cost for you.

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