I’m a Mechanic: These Are the 7 Worst Car Maintenance ‘Hacks’ That Could Cost You Hundreds or Thousands

Close up hands of unrecognizable mechanic doing car service and maintenance.
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For many people, cars are an essential part of life. But having a car comes with a whole host of responsibilities, including potentially expensive maintenance and repairs.

According to AAA, the average cost of vehicle maintenance can set you back around $792 a year. Considering this, it might seem like handling these issues yourself is the better — and cheaper — option than spending money at the auto repair shop.

While it’s definitely possible to save money by doing certain types of routine maintenance yourself, some things should be left to a professional. Here are some of the worst pieces of car maintenance advice that could end up costing you hundreds or thousands of dollars in the long run, according to automotive experts Peter Zavarelli and Ankit Dhadwal.

Refurbishing a Dead Car Battery

Most car batteries last a few years, though some might last longer than that. Eventually, though, you’ll need to replace yours. But if you decide to refurbish the battery instead, you could be looking at expensive repairs or maintenance down the road.

“I have observed that some car owners choose to fix their dead car batteries themselves and turn them into refurbished batteries. In general, a brand-new car battery can cost anywhere from $150 to $499, depending on various factors such as the brand, power, durability, and longevity. On the other hand, a refurbished car battery usually costs between $49 to $120, depending on its condition, which is cheaper than a new one,” said Dhadwal, an experienced auto industry professional and founder of Mount Shine.

Make Your Money Work for You

“Car owners often attempt to save money by refurbishing dead car batteries on their own,” he continued. “They do so by replacing the battery plates, acid, separator, and terminals, assuming that only one or some of these parts are not functioning properly. However, this often leads to more problems and expenses than expected. In many cases, it would be much easier and cost-effective to simply purchase a new battery instead of attempting to refurbish the old one.”

Changing the Oil but Not the Filter

Another expensive car maintenance hack that could cost you thousands is changing your oil without also checking the oil filter to see if its needs a replacement. People sometimes skip this essential step because they simply forget. Other times, they’ll replace the filter with a cheaper alternative to save money.

“What ends up happening is the oil is no longer properly filtered when using an old plugged-up engine oil filter or a cheaper filter, and the oil pressure can lower due to a restriction in the used old engine oil filter, or the oil is not filtered properly when using a cheaper filter, which can cause internal engine damage,” said Zavarelli, an automotive repair expert at JustAnswer Cars. “The internal engine damage can result in the engine itself needing to be replaced, which can cost over $4,000 in many cases.”

Repairing Car Shocks Yourself

Car shocks, or shock absorbers, are designed to support the vehicle’s suspension system and ensure a smooth ride by absorbing various vibrations and bumps on the road. They’re a vital part of any vehicle’s system, but they can wear out. When this happens, it can affect the safety and control of your vehicle, not to mention comfort. Shocks need to be replaced roughly every 50,000 to 100,000 miles, depending on your driving habits and the roads you tend to drive on.

Make Your Money Work for You

“Car owners often attempt to save money by fixing their car shocks themselves, but this can often lead to more problems,” said Dhadwal. “Shocks are a vital component of a car’s suspension system and should only be handled by experienced professionals. A single mistake can result in higher car maintenance costs and even affect auto insurance rates. It’s important to leave the job to the experts who have years of experience in dealing with cars.”

Relying on ‘Fix a Flat’

“When a tire is low on air, many people will purchase a can of ‘fix a flat’ or [something] similar to air up the tire instead of using air,” said Zavarelli.

While this can be a temporary fix, relying on it for too long can irreparably damage the tire or tire pressure sensor.

“The sealant should only be used in an emergency to get you by until you can have the tire repaired,” Zavarelli said. “This can lead to the tire itself needing to be replaced and/or the pressure sensor, which can cost anywhere from around $100 to over $400 to have repaired.”

Replacing Wiper Blades Yourself

Like other car parts, wiper blades eventually need to be replaced. Many people do this themselves, but improper installation could cause more harm than good. This is especially common when you use wiper blades that aren’t the right size.

“I have seen many customers use an incorrect size or a cheaper blade that does not fit properly to save a few dollars,” said Zavarelli. “What tends to happen is the blade can come off or fail prematurely, which can cause deep scratches in the windshield once the blade does fall apart or come off… [this] will result in the windshield needing to be replaced. This can cost over $400 in most cases to have it replaced.”

Of course, installing the wrong blades could also be a safety hazard.

Building Your Own Transmission

Your car needs a working transmission in order to operate properly. Transmissions can last for several hundred thousand miles before it needs to be replaced. Some people will attempt to fix or build a new transmission themselves to save money at the mechanic.

“Building a transmission is an expensive process involving multiple factors. Repairing a transmission requires significant labor as technicians must disassemble and reassemble the transmission, which is time-consuming and requires specialized skills,” said Dhadwal. “Every part must be inspected and replaced if required, and there are about a dozen critical clearances and adjustments that must be made. After reassembling the unit, it must be thoroughly tested to ensure that the problem is fixed.”

While an experienced individual might be able to build a new transmission properly, anyone else should go to a professional or risk losing out on thousands of dollars.

“I will not advise anyone to attempt fixing or using a DIY hack to solve issues related to car transmissions. The cost of repairing a car transmission can range from $2,500 to $5,000, and any errors during the process can lead to having to replace the entire system. This can result in additional costs that one may not be prepared for,” said Dhadwal.

Switching Out Gearbox Fluids

Gearbox oil deteriorates after a while. Left unchecked, it could severely damage your vehicle’s internal systems, requiring expensive repairs and parts replacements. But replacing the fluids on your own could also be costly.

“When changing out gearbox fluids, many customers will use either the incorrect fluid type or incorrect fluid weight because the fluids they find are cheaper. Using incorrect fluid types and weights will ultimately damage the gearboxes internally, which in the long run can lead to the gearboxes needing to be repaired or replaced,” said Zavarelli. “These types of repairs can cost [thousands] of dollars to resolve. This also goes for the engine oil weight; if an incorrect weight is used, that can lead to damage in the engine itself.”

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