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For some people, car maintenance is easy. They follow the little schedule that comes with the vehicle manual, get their oil changed on time, and rotate their tires every 6,000 to 8,000 miles. Others aren’t quite so mechanically savvy; they know where the gas tank is, but that’s about it (and if they live in New Jersey, they might not even know that).

We’ve got good news for the irresponsible people and bad news for the responsible ones: Regardless of which group you fall into, there’s a pretty good chance you’re messing something up. We looked into a few of the most common chestnuts of car maintenance wisdom—only to find that they’re often misleading or outright wrong.

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To extend your vehicle’s lifespan, optimize handling, and avoid overspending at the pump, keep the following misconceptions—and the actual tips that follow—in mind. We also included our picks for car products that actually improve performance, save fuel, and keep you safe on the road.

1. “Get the cheapest gasoline you can find. It’s all the same stuff.”

Typically, if you’re looking for gas, you’re looking for the cheapest fuel available. There are dozens of smartphone apps designed to help drivers find inexpensive gasoline, and if you’re on the road and you’ve got the option of paying either $2.56 or $2.53, you’ll make the obvious decision.

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However, gas formulas aren’t identical, and the detergents in some products can actually affect the long-term health of your engine.

The oil industry’s “Top Tier” program is a gasoline performance standard, and it actually seems legitimate. To get the designation, gasoline marketers have to maintain certain detergent levels in their products. The program is at a fairly wide variety of gas stations, from Amoco to Valero (unfortunately, there aren’t any gas stations that start with a Z that are a part of the program).

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In 2016, an independent laboratory hired by the American Automobile Association found that Top Tier gasoline reduced engine deposits substantially. Granted, a motor club’s proprietary report isn’t exactly peer-reviewed research, but the full report notes that Top Tier gasoline isn’t significantly more expensive than alternatives—it averages about three cents more per gallon—and it’s certainly cheaper than a new engine.

If you’ve made the mistake of filling your car up with the cheapest possible gasoline, consider investing in a quality fuel system cleaner.

As the name implies, a fuel system cleaner clears sediment from fuel injectors, carburetors, intake valves, and combustion chambers, improving engine performance and restoring power. If you’re noticing poor fuel economy on an older vehicle and you’ve already checked your air filter, this is your next logical step.

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Techron’s Complete Fuel System Cleaner works best when used every 3,000 miles or so (in other words, with every oil change). Incidentally, it’s also an effective product for small gasoline engines—lawn mowers, motorcycles, and anything else that needs an occasional cleaning.

Techron Concentrate Plus Fuel System Cleaner, $11.92 on Amazon

2. “For a performance boost, go with premium gas.”

But while you’re pumping up, don’t make the mistake of putting high-octane fuel into a vehicle that doesn’t need it. We know, we know—that big “premium” sticker looks pretty tempting, but if your car isn’t designed for higher octane fuel, you’re wasting your money.

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According to Kelley Blue Book, high-octane (or “premium”) fuel reduces an engine’s “ping” or “knock”—basically, the fuel/air mixture that powers the pistons can combust before it’s supposed to, creating a pinging or knocking sound—but relatively new engines that aren’t designed to take advantage of the higher octane rating will simply burn off the excess.

To be clear, high-performance engines need higher octane gas to run efficiently and safely, so check your owner’s manual—but if your vehicle’s designed to use 87-octane fuel, that’s what you should use.

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With that said, if you have an older vehicle, carbon deposits in the engine might actually make the high-octane fuel worthwhile. That’s because the engine’s octane rating rises over time as the deposits raise the combustion ratio.

Essentially, the engine becomes less efficient, and uncontrolled combustion messes with the engine’s balance, causing pinging. By adding premium gas to an older car, you’re counteracting the carbon deposits, so the car will be able to run without pinging like crazy.

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If you’re considering the fuel upgrade, check with your mechanic before making the switch; while premium gas won’t harm a lower-octane engine, it won’t be too kind on your pocketbook, so you’ll want to make sure that you’ll actually benefit from the upgrade. For newer vehicles, simply follow the fueling instructions in the user manual.

Instead of paying for premium, improve the quality of your gas.

STP’s gas treatment system is slightly more affordable than the last fuel system cleaner we mentioned. It basically functions the same as the fuel additives that gasoline companies use to improve their products.

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Add it to your gas tank and it fights carbon and varnish deposits while removing water, preventing your fuel line from freezing in the winter. It’s made with jet fuel—if that’s not a selling point, we don’t know what is.

STP Gas Treatment Value Pack, $3.57 on Amazon

3. “Tire maintenance is simple: Check tread depth, then you’re good to go.”

If you’re paying any attention to your tires, good for you. According to one 2012 study, about 13 percent of American automobiles have at least one bald tire, and few events are scarier or more dangerous than a blowout.

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However, tire inflation—or lack thereof—is also a big problem. A National Highway Traffic Safety Administration study of tire inflation pressure showed that 12 percent of all somewhat-aged passenger vehicles (2004–2011 models) in the United States have at least one tire under-inflated by at least 25 percent.

That was true even for vehicles with tire pressure monitoring systems, so if you’re waiting for that little light to warn you that it’s time to air up, think again.

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We shouldn’t have to tell you this, but it’s really, really important that you keep your tires properly inflated.

“Properly inflated tires will reduce frictional force on the tires, thus reducing heat. This will increase the life of the tire,” says Robert Dillman of Dillman Driving School in Florida. “Properly inflated tires also increase the tire contact patch and provide a consistent and stable sidewall in the event your vehicle slides. It reduces the tire’s propensity to roll under the wheel in hard turning or skidding and reduces tire failure or de-beading.”

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Hopefully, you already know the basics. Check the pressure when your tires are cold, never over-inflate, and plan on adding air every month or so as the tires naturally lose pressure.

Next question: Should you inflate to the PSI on the tire or on the sticker on your vehicle’s door? Well, that depends on who you ask—car manufacturers insist on following the door sticker. Dillman recommends using the number on the sidewall.

“Inflate your tires to the recommended PSI found on the sidewall, not on the vehicle sticker,” Dillman says. “Tires are made with different ply materials, heat ratings, and compound densities. Inflating to the vehicle sticker will provide the ride quality initially intended, but inflating to the sidewall max recommendation provides numerous more benefits.”

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This is a controversial subject, even among driving experts. The Star Tribune‘s Paul Brand noted that filling to the max PSI will improve handling to an extent, but it will also reduce fuel efficiency and tire tread life. Because car weights vary, we’d stick with the number listed on the door sticker.

While we’re on the subject, a quick car hack: If you’re stuck with a “low tire pressure” warning light and you don’t have a pressure gauge handy, you can touch each of the tires with your hand to find the culprit. Since part of the tire’s job is to reduce friction with the road, an under-inflated tire will be significantly warmer than properly inflated tires.

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Of course, this is only an emergency measure, as it can’t help you determine how much air to add. The best course of action is to buy a cheap tire gauge during your next visit to the gas station and stash it in your glove compartment so you’ve got one when you need it.

To keep your tires properly inflated, invest in a high-quality tire gauge.

You’ve got two options here: A digital fuel gauge or a classic pencil gauge. They’ve each got their advantages—with a digital gauge, you’ll get an exact readout every time, which should help you obtain identical pressure for all four tires.  However, digital gauges require batteries, so they’re inherently less reliable.

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Milton Industries’ S-921 is our pick for a high-quality pencil gauge. Made in the U.S.A. with machined parts, it features a built-in deflator valve, a single-chuck head, and an easy-to-read white indicator bar. Press it evenly into your tire stem, and you’re ready to start pumping.

Milton S-921 Pencil Tire Pressure Gauge, $6.98 on Amazon

If you opt for a digital gauge, consider the Accutire MS-4021B. It’s incredibly simple to use, and the heavy-duty construction ensures years of reliability.

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The rubber-coated handle won’t slip out of your grip, and an automatic shutoff system prevents you from accidentally deflating your tires. Most importantly, it’s accurate to 0.5 PSI, and it runs for years on three Maxwell LR44 (or equivalent) coin-cell batteries.

Accutire MS-4021B Digital Tire Pressure Gauge, $10.47 on Amazon

While you can air up your tires at most gas stations, we’d recommend keeping an inflator in your vehicle.

You never know when you’re going to see that “low tire pressure” warning light, and if you’re particularly unlucky, it might pop on when you’re miles from the next gas station. Besides, many stores charge for access to their air pumps, and we’d rather store a single compressor in our trunk than keep a bunch of quarters in our center console.

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The EPAuto Portable Air Compressor Pump has a built-in digital tire gauge, and it hooks up to your car’s 12V port. Set the desired PSI, and it automatically shuts off after reaching that pressure marker, preventing overinflation. Note that it doesn’t support truck tires.

EPAuto Portable Air Compressor Pump, $34.87 on Amazon

Another option is the Audew Portable Air Compressor Pump. Again, it hooks up to your 12V port, and it automatically shuts off when it reaches the desired pressure marker.

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It also comes with a variety of tips, so you can use it to pump up bicycle tires, basketballs, and virtually anything else that requires air. We love the space-saving flat design. With that said, both of these compressors basically work the same way—choose whichever design you prefer, then enjoy the peace of mind that comes from a well-inflated set of tires.

Audew Portable Air Compressor Pump, $35.99 on Amazon

4. “To avoid wasting gas, roll down the windows.”

By all means, if you’re cruising at a low speed, roll those windows down and hang your arm out of your yellow 2002 Dodge Neon. How else are you going to impress potential suitors?

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But when you get up to speed, you’ll want to switch over to the AC. That might come as a surprise for those of us who learned in driver’s ed that the AC sucks up more gasoline than a thirsty…uh, gasoline-drinking animal, but modern air conditioners aren’t quite the inefficient horrors of the past.

Using the air conditioner on the highway will consume some fuel, but not much compared to what you’d spend by rolling your windows down. The U.S. Department of Energy recommends running the air conditioner at highway speeds since open windows increase an automobile’s drag significantly, forcing the engine to work harder to maintain speed.

As USA Today noted, there’s another reason to keep the AC on: If you’re comfortable, you’re less likely to make driving mistakes that could lead to an accident.

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Of course, if you’re really worried about fuel efficiency, look to your driving habits. Aggressive drivers can waste up to 40 percent more gas than their calmer contemporaries, according to the EPA. Avoiding road rage—and keeping your attention on your driving—can save you anywhere from $0.28 to $1.13 per gallon, depending on traffic conditions and other factors.

If your air conditioner doesn’t work like it used to, find the problem.

We’re going to assume that your air conditioner kicks on; if not, you might need a new fan, which probably means a trip to the mechanic (unless you want to try to handle it yourself—it’s not that big of a job).

If your air conditioner kicks on but doesn’t seem very cold, you might have a refrigerant leak. The fastest way to find the source of the leak is to use a dyed R134a additive.

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This product from FJC should do the job nicely; it’s designed to seal minor O-ring and gasket leaks, and a visual red dye lets you find leaks in your hoses without damaging your AC system.

FJC 9140 Stop Leak, $9.69 on Amazon

If you’ve had a slow leak for a while, you’ll need to refill your system with refrigerant. Refrigerant—get ready for this—refrigerates your vehicle. Interdynamic’s A/C Pro all-in-one refill system gives you everything you need to tackle that job, including a pressure gauge that will help you avoid accidentally overfilling your AC system. It also comes with a vent cleaner and a kit for stopping leaks.

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Be sure to read the instructions carefully and hook it up to the low-side service port; if you’re at all unsure, ask a mechanic or stop by your local car parts store.

A/C Pro Air Conditioning Recharge Bundle, $64.64 on Amazon

If you simply prefer the feeling of cool air blowing in your face, well, you can get that without actually rolling the windows down. This dual fan set runs off of your vehicle’s 12V port, consuming less energy than your air conditioner while quietly circulating the air. It doesn’t take up much space on your dash, and you can choose from two speed levels.

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This is a great product to keep in your car if you occasionally nap at rest stops, and it’s also an excellent pickup for boats and recreational vehicles.

Excoup 12V Cooling Air Fan, $26.99 on Amazon

5. “If your battery dies, jump-start your car.”

We don’t really think about our batteries until they stop working, but the best practice is to switch out your battery before it fails to start your car.

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AAA recommends testing your battery regularly once it’s three years old.

While some units can last upward of five years in relatively cool climates, factors like heat, vibration, and usage can cause a battery to fail much earlier, so the best course of action is to test regularly and switch out your battery when it’s showing signs of wear.

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If you do find yourself with a dead battery, try to avoid jump-starting your car unless it’s absolutely necessary. Doing so will create a voltage spike that can damage systems in the donor vehicle, even if you follow the proper process for jump-starting (blogger Rick Muscoplat explains the science behind that risk in detail here).

Newer vehicles also have a number of computers which can be easily damaged by sudden surges of electricity.

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A better option is to keep a jump-start pack in your vehicle.

You can pick them up for under $100, and that’s much cheaper than hiring a tow truck. Ideally, you’ll get a starter with a power indicator; check it regularly to make sure that you’re prepared in the event of an emergency.

Our first pick in this department is the NOCO GB40, a compact lithium jump starter capable of providing up to 20 jump starts per charge. It’s spark proof, so you won’t have to worry about accidentally setting your vehicle on fire—that’s a big plus in our book—and it’s equipped with an ultra-bright flashlight, which allows you to signal for help if your battery is completely unresponsive.

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It also has built-in USB ports, so if you find yourself stranded on the side of the road, you’ll still be able to charge your phone and call for help.  Technology’s pretty awesome, isn’t it?

NOCO Genius Boost Plus GB40 Jump Starter, $98.95 on Amazon

For a more portable option, check out this great little unit from DBPower. It’s small enough to fit into your glove compartment but powerful enough to jump-start your vehicle in seconds.

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It also has two USB ports, a DC power output, an LED flashlight, and a compass. The included battery clamps feature an intelligent protection feature that prevents damage from short circuits, reverse polarity hookups, and overcharges.

DB Power Portable Car Jump Starter, $64.99 on Amazon

Oh, and before you pay for a replacement, make sure that your battery is actually bad.

Start by cleaning off any corrosion. You’ll still need to figure out why your battery is corroding, but at least you’ll make it to the mechanic.

While you can handle this job with some soda water (or cola, if you don’t have soda water handy), a commercial battery cleaner has the added benefit of detecting leaks.

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CRC 05023 is a battery cleaner with a built-in acid indicator, and it’s a solid choice; check out the numerous five-star reviews on Amazon. Spray it on, let it foam, and wash it away.

CRC 05023 Battery Cleaner with Acid Indicator, $8.12 on Amazon

After cleaning your terminals, brush them thoroughly. The Schumacher BAF-BI makes this a much faster process. To use it, slide it over each terminal and twist.

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That’s it—it’s not exactly space-age technology, but it’s everything you need to ensure the best possible contacts.

Schumacher BAF-BI Terminal Cleaning Brush, $3.96 on Amazon

Finally, you’ll want to prevent future corrosion by separating your battery cables from the battery chassis. Fiber washers can accomplish this task easily. Here’s a two-pack of colored fiber washers, manufactured to SAE standards, that provide essential protection for your car’s battery by preventing moisture from building up around the posts.

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They’re pre-perforated, so you simply need to slide them on each terminal, then install your battery cables.

Road Power Anti-Corrosion Fiber Washers, $6.07 on Amazon

For best results, apply a small amount of white lithium grease before installing the fiber washers.

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The grease will provide an additional layer of protection from moisture (and therefore, corrosion).

Permatex 80345 White Lithium Grease, $3.99 on Amazon

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