We’d all be a little wiser and a lot richer if we knew some basic things about the cars we drive. Yet we rely on so-called “expert mechanics” to diagnose problems with our vehicles and then fix them. We are often forced to trust that those mechanics are honest enough to tell us the truth about our cars.

Sadly, this is rarely the case. In fact, lots of shady mechanics go out of their way to treat their customers like mushrooms. That is, keeping them in the dark and feeding them crap.

Many mechanics know some basic truths about cars that they would never want any of us “common folk” to know. Instead, they prefer to deal with ignorant people that they can sell lies to and charge a lot of money. Fortunately, a little knowledge goes a long way. Here are 12 things about your car that your mechanic does not want you to know.

12. The Check Engine Light

The most common reason for the dreaded “check engine” light being lit up on the dashboard is because the gas cap is not screwed on tight enough. Sad but true. A sensor in the car responds when the gas cap is not secured tight enough and extra oxygen seeps through the gas line. The light almost always goes off once the cap has been tightened, or the entire tank of gas has been used and is empty.

Remember this the next time the check engine light pops up. Before you panic, give the gas cap a few extra turns with your hand. You could save yourself a big headache and expensive bill from a mechanic.

11. Car Batteries Almost Never Need To Be Replaced

Some mechanics love to tell you that your car battery has died. As in, time to buy a new one. However, most problems with car batteries are actually caused by the wires connected to the battery and not the battery itself.

Over time, those connections can become corroded. That impacts the amount of power getting from the battery to the car. The fix for this problem? A can of Coca-Cola. Take some Coke and pour it on the area where the wires connect to the car battery and the Coke will eat away at the corrosion. Some CLR also works well. This is a quick and easy fix that need not involve a mechanic. Just watch a YouTube tutorial and you should be fine. It can save you on the cost of a new car battery. Also, many “dead” batteries can simply be recharged and return to normal working condition. They needn’t be replaced.

10. Most Garages Lie About Rotating Your Car Tires

So, you’ve brought your car to the garage and paid a little extra to have the tires rotated. After all, the mechanic did advise that the tires should be rotated, to ensure the tread on them wears evenly. The only problem is that when you get the car back, you can’t tell if the tires have been rotated at all. All your tires look the same anyway, right?

Some shady garages won’t actually bother to rotate the car tires. They will definitely tell you they did, though, and happily take that $50 out of your pocket. Furthermore, there is a raging debate about whether rotating the tires is really needed. Some studies show that tires wear out just as fast whether they are rotated or not.

To ensure that your car tires are actually rotated, take a piece of chalk and mark them before bringing the car to a garage. Write “FL” on the front left tire, “RR” on the rear right tire, and so on. Remember, your tires are supposed to be rotated front-to-back, not side-to-side.

9. You Probably Don’t Need That Oil Change

Most mechanics will tell you that your car needs an oil change every 3,000 miles. That’s not necessarily true. Most car experts agree that oil should be changed once every 7,500 miles at the earliest. However, many folks in the auto industry will tell you that an oil change every 10,000 miles or 16,000 kilometers is also perfectly acceptable. A lot of it depends on the make and model of your car.

What is even more important than an oil change is to ensure that your car doesn’t run out of oil. Keeping the oil topped up in your car is much more important than changing the oil itself. While mechanics will tell you that dirty oil is bad for your car engine, the reality is that engine oil burns off and evaporates over time. That means dirty oil is not that big of an issue for modern cars. However, the oil does get lower over time. If you’re putting off an oil change, at least check the dipstick and top up the reservoir if needed.

 8. The Biggest Problem With Brake Pads Is Rust

Do you hear the brakes on your car screeching? Is it freaking you out? It shouldn’t be. The biggest problem with brake pads, and the main reason they screech, is rust. This rust can be quickly and easily scraped, brushed, or blasted off. You probably don’t need to shell out a lot of money for new brake pads.

In fact, most people can scrape the rust off their brake pads themselves with the help of a YouTube video to guide them. Most garages will also take the rust off for a fairly cheap fee. The trick is getting the mechanic to tell you that the problem is rust on the pads. They will sometimes try to sell you on a whole set of new pads (and maybe shoes and rotors too). Take the time to learn a tiny bit about how brakes work, and don’t believe them.

7. In Most Cases, All-Season Tires Will Do

Unless you live in northern Canada (or another very snow locale), chances are you don’t need winter tires. The fact is that a good set of all-season tires will do most people just fine. Yet the automotive industry is making a killing by convincing people that they need two sets of tires – one for spring and summer and another for fall and winter driving.

Mechanics are making a good deal of money simply taking off one set of tires and putting on the other. Some garages also charge a fee to store the set you’re not currently using. This is a racket, plain and simple.

Tests have shown that all-season tires have sufficient tread to stop vehicles in most winter driving conditions. These tires will still work great during the summer too. Don’t get us wrong, winter tires can be extremely helpful. However, they are only truly necessary in the most extreme winter driving conditions. If you live in Buffalo, get winter tires. If  you live in Seattle, skip them. And if you live in Texas, why’d you even read this section?

6. “Free” Inspections Are Anything But Free

So your local garage is offering a free bumper-to-bumper inspections of your car, no questions asked? Be careful. While the thought of a free inspection sounds nice, you need to remember that the garage has an incentive of their own — to find things to fix. Or maybe invent things to fix, if they are particularly unethical. Simply put, it’s an easy way for a mechanic to drum up business.

We guarantee that you’ll never bring your car in for a free inspection and hear a mechanic say “Looks great. I don’t see any problems. Take care, now.” More likely that the mechanic will come back to you with a laundry list of needed repairs, scheduled maintenance, and/or upgrades. Don’t fall for this scam. Bring your car into a garage when it needs a repair only. Avoid anything involving a garage that is allegedly free.

 5. Lube Jobs Are Not A Necessity

It seems like places are popping up all over that offer quick lube jobs. People can pull in with their car and in 15 to 20 minutes have their engine oil replaced, the engine parts lubricated, and the tires filled with air. Wow! What a waste of time and money. The reason these types of places are popping up all over the place is because they are a cheap and easy way for people to make money off unnecessary services.

We’ve already gone over when cars should really have their oil changed, and most people are capable of putting air in their own tires. Which brings us to the lube jobs. Most cars never need to have their engine parts lubricated. They are either already lubricated or don’t require lubrication. When you pay for a lube job, you’re paying to have a teenager smear gunk around under the hood of your car. Save your money, people.

 4. Brake Pads Don’t Need To Be Replaced Until They’re 90% Worn

The mechanic comes out to meet you in the waiting room. He tells you that the brake pads on your car are 50% worn and should be replaced. You agree, because you don’t know any better. Cha-ching! your cost goes up again. Except brake pads don’t actually need to be replaced until they are 90% worn. A brake pad that is 50% worn is only half-way through its usable life.

Keep the brake pads until they are at least 90% worn. The problem with brakes is that people consider them as a major safety factor (and they are). So you don’t want to take any chances with them, right? Mechanics prey on this fear. Trust yourself. If there are any problems with your brakes, you will know it right away and can get them checked. Keep your brake pads as long as you can. It will save you money in the long run.

3. Rustproofing A Car Can Cause More Rust

Given a choice, most drivers would avoid unsightly rust on their car. After all, a rusting car looks pretty trashy. However, over time, some rust on your vehicle is inevitable. Especially on cars that are approaching their tenth birthday. Here’s the rub: there is very little evidence that rustproofing a car actually prevents rust.

To the contrary, there are some studies that show rustproofing can actually lead to more rust on a car. This is because ice and road salt tend to stick to the rustproof coating that is sprayed underneath a car. Rustproofing is popular in the northern U.S. and in Canada, but it often provides no real benefit to your car. It can help a bunch of unwanted ice and salt gets trapped underneath a car, causing more damage in the long run. You’re better off giving your car regular car washes.

2. You Can Change Your Brake Pads Yourself

As we’ve established, swapping out (still usable) brake pads is big business for mechanics. This is because replacing brake pads is relatively quick and easy, but can come at a pretty painful cost. In reality, changing brake pads is so easy that most people can do it themselves. There are plenty of websites and videos online that show how to quickly, easily, and safely change a vehicle’s brake pads.

While you might shy away from doing this job yourself out of fear of screwing it up, there really is no reason to worry. People will know instantly if they have not put their brake pads on properly. In only a half hour, you can change their brake pads yourself and save money in the process. Like we said, though, only do it when the brake pads are 90% worn.

1. There Is A Guide That States The Correct Labor To Charge For Every Repair

There are many lists published every year that detail the number of labor hours that a garage should charge for each job they offer. Trust us when we say that your mechanic does not want you to know this. That’s because most mechanics want the freedom to charge their customers as many hours (and as much money) as possible. Unsurprisingly, they rarely charge the standard rate.

Arming yourself with information on the correct amount of time and money that should be charged for each repair will empower you and give you leverage. The next time you are at a garage, ask for a breakdown of the labor hours you’re being charged for, then ask to see the labor hours in the guide. If the mechanic doesn’t want to show you, starts making excuses, or if the hours don’t match, it’s time to take your business someplace else. That mechanic you are dealing with is neither trustworthy nor reputable.


This article was worked on by a variety of people from the Autoversed team, including freelancers, editors, and/or other full-time employees.