Can A Bad Wheel Bearing Hurt Your Gas Mileage? Here’s What You Need To Know

Wheel bearings are integral parts of your car’s suspension system. They connect the axles to the wheels and allow smooth movement with minimal friction. They also help support the car’s weight and assist with braking and cornering.

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There are two primary types of wheel bearings: cone-shaped bearings that require routine maintenance, and modern sealed bearings. Both are durable, but not immune to wear and tear or damage. 

Cone-shaped or tapered bearings are more common on older vehicles and those that are front- or rear-wheel drive. On these cars, the grease-packed cone-shaped bearings are located on the axle that doesn’t connect to engine power. They require more maintenance than sealed bearings and must be repacked with grease periodically, depending on your make, model, and driving habits. They’re extremely messy, but easy to work on, and can be easily and inexpensively replaced when they fail.

In contrast, modern sealed bearings may be found on both driving and non-driving axles. They don’t generally require maintenance and are designed to last roughly 80,000 to 100,000 miles. They usually come in one assembly, and when they fail, you must replace them, too. 

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When wheel bearings fail, they can cause fairly serious issues, including a drop in fuel mileage. If you’re wondering why, stick around. As a former professional mechanic who specialized for years in suspension work, I’ll explain why a bad bearing may cause your gas mileage to plummet, give the signs of a faulty wheel bearing, and touch on replacement costs and procedures. 

We mentioned that wheel bearings are primarily responsible for facilitating the smooth movement of your car’s wheels with minimal friction. That’s a vital responsibility, because the wheels’ free movement is essential for smooth engine performance — it also helps your braking system work properly and contributes to comfortable handling. And when wheel bearings fail, they begin to lose that ability to keep the wheels moving smoothly.

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Wheel bearings typically fail due to outside moisture and debris. Over time, these contaminants can work their way into the bearing, and even modern sealed bearings are susceptible to this type of damage. Bearings can also fail as the result of simple wear and tear. In these cases, outside impurities don’t cause the failure. Rather, the bearing races — the bands or tracks in which the ball bearings sit and spin — begin to degrade, causing metal flakes to gunk up the grease.

Regardless of the reason, a wheel bearing’s failure can cause a range of issues for your car, which leads us back to drops in fuel mileage. Because a bad wheel bearing hinders the wheel’s ability to move freely, friction and heat — which represent a loss of power — develop. The engine must work harder to overcome that friction, which can translate to worse gas mileage and a host of other problems.

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Besides a drop in fuel mileage — which also can be caused by other problems — a faulty wheel bearing typically displays a handful of other symptoms. One of the most characteristic signs of a bad wheel bearing is a loud humming, grinding, or groaning noise coming from one side of the car as you drive. The symptom is usually magnified when you turn, and may be accompanied by clunking or rumbling noises. Remember, though, that your car can make a lot of strange sounds when there’s a problem. So you can’t rely 100% on these noises to diagnose a faulty wheel bearing.

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Besides strange sounds, a bad wheel bearing can cause a few other issues. Uneven tire wear is a common symptom of suspension problems, including a faulty wheel bearing. It’s not usually enough on its own to diagnose the problem, but if you notice your tires wearing unevenly, it’s a good sign that something is wrong with your wheel alignment, suspension system, or tire pressure. Other symptoms of a bad wheel bearing can include things like your car pulling to one side, vibrations in the steering wheel, and the appearance of your ABS dashboard warning light.

Considering that bad wheel bearings can cause many problems also associated with other mechanical malfunctions, it isn’t always easy to diagnose them. Fortunately, if you suspect a bad wheel bearing, there is a fairly simple way to check.

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Put your car in park, then place an automotive jack under its frame rails or pinch welds and lift it off the ground a few inches. Place one hand on top of the tire at the 12 o’clock position and your other hand on the bottom at 6 o’clock. Then rock the tire back and forth, up and down. If you feel a popping or wobbling sensation, there’s a good chance you have a faulty bearing — if it’s especially bad, you may even see some movement inside the wheel around the hub and axle. 

You can also try spinning the wheel freely when the car is off the ground — the wheel should spin relatively effortlessly if the bearing is in solid condition, while the wheel will be more difficult to spin and may make some strange noises if the bearing is bad. Note that it’s important that you shake the wheel correctly, as shaking it from the sides is usually how you test tie rods — although sufficiently degraded bearings can cause side-to-side movement also — while lifting the vehicle from a control arm and shaking up and down with a pry bar is how you test ball joints.

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If you have a bad wheel bearing, replace it as soon as possible. The cost depends on factors including your car’s make and model, and your area’s labor rates.

Cone-shaped and tapered bearings usually cost around $10 to $20. These replacements are fairly straightforward but extremely messy, as you have to pack the bearings with grease manually. If a professional mechanic performs the service, you’ll most likely pay around $75 to $150 per bearing.

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Sealed wheel bearings and pressed-on bearings are more expensive to replace due to both the price of parts and the extra labor required. A new bearing and hub assembly can cost from $75 to over $300, depending on the vehicle and part brand. Factor in the mechanic’s labor and you’re likely looking at another several hundred dollars. Furthermore, you may need a wheel alignment afterward — especially if the bad bearing is on the front axle and you have uneven tire wear — which may add another $50 to $100.

Considering the costs, you may wondering if you can replace wheel bearings yourself. These are not the most difficult repair jobs, but they’re also not one of the easiest DIY auto projects for beginners. They’re a mid-level task and should be relatively straightforward for experienced home mechanics and DIYers, providing you have access to the proper tools. But if you’re a complete car novice, you’re probably better off visiting a pro.

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