Whether it’s a musty smell or the result of a spill, here’s how to fix it—and keep it from happening again

“Sorry to tell you this, Keith, but your car stinks.” My friend’s words confirmed my suspicion: Yes, the used station wagon I’d just bought had a clean vehicle history report and all its service records—but it also had a serious odor problem. To make matters worse, I was supposed to drive three other people to an event later that week.

If you’ve ever been in a similar situation—wrinkling your nose at the scent of your own vehicle as your thoughts drift to the “smelly car” episode of “Seinfeld,” where Jerry’s BMW inexplicably smells “beyond B.O.”—we have good news for you: That stench might not be your fault. And even if it is, you can fix it. We’ll tell you how.

Consumer Reports’ in-house mechanics—the same ones who keep our fleet of test vehicles running smoothly and sparkling fresh—gave us tips you can use for your vehicles, even if mice made a home under the hood or you left the sunroof open before a rainstorm. We also reached out to car wash operators, cleaning product manufacturers, and car interior designers to find out how they tackle odors.

Here’s what you should do.

Those nooks and crannies for cups and change can accumulate crumbs and spills that start to smell over time.

Before he came to CR, auto technician Mike Crossen worked at car dealerships where he encountered plenty of unpleasant odors in customers’ cars. The culprit was often obvious—spilled food, dirty gym clothes, or cigarette smoke. To prevent those odors, there’s an easy solution: Keep your car clean.

“Simple regular cleaning helps a lot—not allowing the smelly things to accumulate in the car in the first place,” he says. Toss any leftovers or trash before they can stink up the car, and wipe up or vacuum any dirt you’ve tracked in as soon as you can.

Some odors are more elusive, however, and require more effort to diagnose. “Water leaks, blocked AC drains, not changing the cabin air filter—these can all lead to unpleasant smells,” Crossen says. But fixing those problems requires more effort. That’s why he recommends using the process of elimination to find where the smell is coming from.

Search under seats for old french fries or cereal, for example. Check the cup holders for spilled coffee. Remove the floor mats and shampoo them at a hand car wash or at home using a solution of water and detergent (more on those below).

While the floor mats are out, it’s time to vacuum the carpets. Before vacuuming, sprinkle them with baking soda and let them sit. Make sure the carpet is dry, or the baking soda will clump.

Once you’re done, leave an open can of coffee inside the car overnight—a trick we learned from a car wash owner. In addition to having a pleasant scent in their own right, coffee beans act as a deodorizer.

Even if you use a seat cover, your furry friends can leave smells behind.

For cleaning interior surfaces, Crossen and others recommend cleaners meant specifically for cars, but some household cleaners will also work. When we interviewed Jeff Stout from Yanfeng, the world’s largest supplier of automotive interior parts, he said that isopropyl alcohol is a safe way to kill any germs on a car’s interior surfaces. In fact, it’s what Yanfeng uses in its own factories. “We will use that to clean smudges or any kind of last-minute details before we ship the product,” he told us.

But don’t use bleach or hydrogen peroxide, because they are likely to damage your car’s upholstery. Likewise, ammonia-based cleaners can damage the anti-glare and anti-fingerprint coatings on car touchscreens. Simple Ivory soap and water will do the trick on leather, according to Dara Ward, a spokesperson for automotive leather supplier Katzkin. Don’t scrub too hard, because you may wear off your leather’s protective finish.

As far as cleaning cloths are concerned, we recommend using clean microfiber towels because they won’t scratch delicate surfaces or leave lint behind. That’s especially true on many newer cars, which have shiny black plastic interior trim pieces that are extremely easy to scratch.

Your car's heating or AC system might be responsible for some persistent odors.

If the air coming out of your car’s vents smells like a high school locker room, the problem likely has to do with your climate control system. “What you’re probably smelling is the condensation that comes from the evaporator inside your heating and cooling system,” says Jake Fisher, Consumer Reports’ senior director of auto testing. “Basically, water collects in that area and, if it sits long enough, creates the musty smell.”

You can fix the problem yourself with AC disinfectant you can buy at an auto parts store, or with Lysol aerosol spray. First, turn on the car’s interior fan on the low setting and open the car’s windows. Then spray the disinfectant into the AC intake vents, which can be found at the base of the exterior side of your windshield, near where your wipers are located. For more details, read our complete guide to fixing a musty AC.

While you’re at it, change your cabin air filter. This filter keeps the air inside the car free of allergens and contaminants and is usually accessed through the glove box. Some are simple to reach; others aren’t. Dealers often charge a lot more than the cost of the filter itself, so it’s a good idea to do it yourself if you can. Instructions can often be found in the vehicle owner’s manual. John Ibbotson, CR’s chief mechanic, says YouTube instructional videos can also be helpful.

You may have heard of “odor bombs,” also known as foggers. These aerosol cans automatically spray a scent while the vehicle is unoccupied. After a few hours, the smell is gone—or at least that’s what the advertising says.

Crossen warns that many of these products simply mask a smell with another scent. He says to look for ones that include chlorine dioxide as an ingredient because this chemical can actually eliminate odors.

Sunroofs have drains that can get clogged. If you don't clean them out, a nasty odor might develop.

Still smelly? In most cases, Crossen says, DIY cleaning is just fine. But if that smell doesn’t go away, it may be time to reach out to a detailer—or even a mechanic.

A professional detailer may have special tools that can outperform what you’re able to do at home. For example, an ozone generator emits odor-destroying ozone gas that can permeate every corner of your car’s interior—even the ones you can’t reach with a cloth. “Ozone machines work great to eliminate lingering odors,” says Crossen, who prefers them over odor bombs. If you choose to use an ozone machine yourself, make sure to read the instructions because inhaling ozone gas can harm the lungs and exacerbate breathing problems.

If your car has a moldy, musty odor, it could be the result of a blocked drain—from either your air conditioner or your sunroof. First, you should check for and remove any leaves or obvious debris that are blocking the sunroof drains, which you can find by opening the sunroof and looking down at it from above. The drains are usually at the corners of the black rubber gasket that surrounds the opening. Be gentle because damaging the gasket could cause leaks. CR’s mechanics say to beware of online tutorials that tell you to use compressed air to clean a sunroof drain; that can cause damage. If it’s your AC, you might even hear sloshing sounds when you turn. In either case, a trusted mechanic should be able to help.

Occasionally, our test cars develop the telltale odor of a decaying rodent. That’s because mice and other creatures like to make homes inside cars—especially if they aren’t used often. You can read our tips on how to keep that from happening, but if it’s too late, your car might need a serious cleaning.

The same goes if your car’s interior got really wet—either from a blocked drain or from forgetting to close a sunroof or windows during a rainstorm. Remediating water damage often requires tools and skills beyond what most people have in their own garages, and not doing the job right could have serious consequences.

“Water and mold or rodent problems can cause health issues, and need to be dealt with accordingly,” says Crossen. “Interior panels may need to be removed or replaced, and if there is mold accumulation, it needs to be cleaned with specific cleaners that work on mold.”

On most cars, this is where you spray the AC cleaner.

If you smell something sweet or fishy coming from your vents, it could be a sign that your car’s heater core is bad. Those odors may be due to leaking coolant, and it’s a sign you need to fix the problem right away. Otherwise, your car may lose the vital coolant that keeps your engine from overheating. It could even lead to engine damage.

As it turned out, my musty wagon was suffering from a blocked sunroof drain. The cabin air filter was filthy, and—sure enough—I found fur from the prior owner’s dog underneath the floor mats.

The solution was easy enough: I had a mechanic clean out the AC drain the next time the car was in for service, then I gave the carpet a good shampooing and changed out the cabin air filter by myself. Total cost? Under $100. And I got it smelling clean and fresh before anyone else noticed.

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Consumer Reports is an independent, nonprofit organization that works side by side with consumers to create a fairer, safer, and healthier world. CR does not endorse products or services, and does not accept advertising. Copyright © 2022, Consumer Reports, Inc.

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