How to Keep Your Car Mirrors from Fogging Up

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Close up of a car's side mirror glass that is wet and fogged up

The mirrors on the side of your car are easy to take for granted. You might not even think about them until they’re fogged up and you can’t see out of them. Once that happens, you’ll likely be forced to pull over and fix the problem. It would be much better if you could keep them from fogging up altogether.

A great way to prevent fog on your mirrors is to keep them clean. Regularly use auto glass cleaner to remove pollen, dirt, and dust from the mirrors. After that, you can apply a secondary film to your mirrors and treat them with fog-repelling chemicals to keep them fog-free.

In this guide, I want to explain how to keep your car mirrors from fogging up. I have a few easy DIY solutions that you can try out. I’ll also give you some information about why fog occurs, and the dangers associated with it.

What Causes Fog?

Fog on mirrors can happen due to a few different reasons. Largely, it’s due to either temperature or moisture content (sometimes both).

Since these mirrors are outside of your car, there’s very little you can do to avoid changing temperatures and moisture. There are always water droplets in the air. The humidity level in your area will tell you how much moisture is in the air.

A road in the countryside with fog visible in the background

High moisture and wildly varying temperatures will cause more fog than the opposite condition will. That’s why you’re more likely to have foggy windows and mirrors when it’s raining.

Another thing that causes the fog to be worse is a dirty surface. You might have noticed that your guest bathroom’s mirror fogs up much more than your master bathroom when a shower is running. If you don’t clean the guest bathroom as much, that’s why.

Tiny particles of dust, dirt, and debris will build up and cling to your mirrors. From there, water droplets can settle on the debris and hang around. This process will cause the fog to get worse.

Close up of a car window glass fully fogged up and blurry

A perfectly smooth, clean mirror will never have fog on it, that’s just how the science works out.

These ideas will come in handy later as I mention a few ways to prevent fog on your mirrors. For a quick list to refer to, fog on mirrors is due to:

  • Dirty mirrors
  • A variation in temperature (between the glass and air around it)
  • High moisture or high air humidity

The Dangers of Foggy Mirrors

If you’re in a rush, you might jump in your car and drive despite having foggy mirrors. This is very dangerous, and a police officer can give you a ticket for it if he notices it.

POV from the driver's side seat of the windows and mirrors covered in fog

If your mirrors are fogged up, you won’t be able to see anything. The mirrors are there to give you visibility around your car without having to rotate your head around. More importantly, it shows you cars in your blind spot that you won’t be able to see by turning your head.

You should never start driving if your mirrors are foggy. It only takes a few seconds to clean them and remove the fog, so it’s not worth the potential risk you’re putting yourself in.

How to Keep Your Car’s (Outside) Mirrors from Fogging Up

Without further ado, I’ll start answering the big question: how do you keep your car mirrors from fogging up? In this section, I’ll talk about 10 easy solutions to this problem — all of which you can do on your own without going to a mechanic.

Avoid Rain-X

Before I give you tips for success, I want to point out something you shouldn’t do. You shouldn’t apply standard Rain-X to your car mirrors. Rain-X is used on your windows to prevent water droplets from lingering.

It creates a lubricious surface where water will become droplets and roll away.

Close up of a car mirror glass full of water drops

With your outside car mirrors, this will actually make things worse. By beading up the water, you’re allowing fog to come to the surface, and the beads can block your view of the mirror.

For reference, I’m saying that you shouldn’t use any water-repelling products from the Rain-X product lines. Later in this guide, I’ll explain which option from Rain-X works better.

Clean Your Mirrors

Before trying anything else, I would suggest starting with a quick mirror cleaning. Remember, fog can be caused when water droplets get stuck on the surface contaminants of your mirror. Commonly, this is fine dust and debris that you can’t even see with the naked eye.

By cleaning your mirrors, you’re removing these contaminants. Since mirrors are finely machined with flat surfaces, this leaves condensation with nowhere to go. In other words, if there’s no dust to cling onto, your windows shouldn’t get fogged up.

A person cleaning the side outside mirros on a car on a sunny day

To clean your mirrors, treat them like a mirror in your home. Use a microfiber towel and Windex. Stick to linear motion and avoid using circles when rubbing in the Windex. Use a separate towel to dry the area using the same motion.

Try to minimize how much Windex you get on your car’s paint surrounding the glass of the mirrors. Windex will melt your topcoat if you leave it around too long without wiping it down.

Some people will use automotive tape to mask off the bodywork around the mirror, but this seems like overkill in my opinion. Just wipe down the body with a towel after to make sure all the Windex is removed — the chemical will airdry exceptionally fast due to the chemistry inside the bottle, so it isn’t a huge concern.

Try Shaving Cream

Believe it or not, shaving cream is a low-cost way to protect your mirrors from the fog. This product will change the surface tension of your mirror, preventing fog from sticking in the first place.

A person with shaving cream on their hands a razor and towel isolated against a white background

The only downside is that shaving cream is water-soluble — that’s how it washes away from your face when you use it for shaving. Since you’ll be using it on outside mirrors, it’s not necessarily the best choice. The shaving cream will wipe away after your car’s first rainfall, so you’ll need to reapply it.

The other problem is that rainy weather usually comes with foggy windows and mirrors, so it’s the worst time for the shaving cream to lose its effectiveness.

Replace Old Mirrors

If you have a very old car, there’s a chance that your mirrors are defective. I know, this sounds like a very strange concept.

Outside mirrors are built with a protective film over the glass. It prevents shattering, scratching, and water buildup on the mirror surface itself.

Side rearview mirror on an old rusty car with the glass element scratched up and worn out

Over time, this film can start to peel up. You’ll notice that your mirror is especially foggy in certain areas, and these areas are usually near the lifted or peeled part of the film.

If you’re in this situation, I would suggest going to a junkyard to find replacement mirrors. Otherwise, you can buy OEM replacements online, but you’ll pay more for them and they might be harder to source from a reputable online vendor. eBay is a great alternative for used OEM parts.

There’s also a chance that mirrors from a different car can fit yours, even if it’s not the same make, model, or year. It’s worth messing around at the junkyard to find something that works for you.

Use an Alcohol Wipe

The option that I’ve used most often is an alcohol wipe. It’s best to use an isopropyl alcohol wipe since it will dry quicker, clean easier, and isn’t overly concentrated. This kind of wipe is used to clean glasses and electronic screens.

Use the wipe and use an up-and-down motion on the glass. You don’t want to use circles, because they can smear and distort the mirror. By using linear motion, you’ll get the best results.

Isopropyl alcohol wipes on top of dressing gauze

This wipe is cleaning off dirt from the surface, and priming it to prevent fog in the future. You should reapply the wipe every month or so, but it might be more often based on when you see fog pop up again.

When you’re using this wipe, try to limit how much you touch your car’s body with the wipe. It’s good for a quick wipe against the body, but it can start melting your topcoat if you let the alcohol soak there for too long.

Again, since the wipes try out pretty quickly, it’s easy to avoid this issue by sticking to isopropyl wipes. If you use more concentrated alcohol on a towel and leave it there, you will damage your car.

Consider Upgrading to Heated Mirrors

If you want to upgrade your mirrors, you can find aftermarket options that feature heating elements on the mirror. Since fog can be due to cold mirrors in a warm environment or vice versa, this will prevent fogging.

It’s especially useful during the winter months. As the ice starts to melt, the added moisture can cause your mirrors to freeze and fog up. These heated mirrors will get rid of ice and prevent fog while you’re warming up your car and driving.

Car mirror heating icon isolated against a white background

Based on the size and shape of your mirrors, this upgrade can be anywhere from $50 to $400.

It’s pretty interesting to see how these mirrors work. Basically, there’s a maze of wire on the backside of the glass. When you turn on the mirror, the wires will start passing electricity through and warming up. This directly warms up the glass itself, heating your mirrors.

Park Inside

Another great way to avoid fogged-up mirrors is to minimize how much time your vehicle spends outside. This means parking in an indoor garage overnight.

Cars parked inside a car parking garageCars parked inside a car parking garage

Doing so will keep your mirrors away from the changing temperatures outside and extra moisture in the air. In a garage, the humidity is lower and the temperature fluctuates less — two conditions that will help keep fog away.

It’s still possible for your mirrors to fog up once you start driving, but it’s less common.

Add a Mirror Film

Another smart addition would be to throw some films over your mirrors. There are a number of options that simply stick onto the glass of your mirror. The purpose is to add another layer of protection.

The added film uses some sort of chemistry to keep the surface tension low and create a smooth surface. Doing so will make sure fog doesn’t stick to the film.

12-Pieces Car Rearview Mirror Film Rainproof Waterproof Mirror Film Anti Fog Nano Coating Car Film for Car Mirrors and Side Windows

12 Pieces Car Rearview Mirror Film Rainproof Waterproof Mirror Film Anti Fog Nano Coating Car Film for Car Mirrors and Side Windows
Car window and mirror anti-fog film

Of course, these films are transparent so you can see through and still use your mirrors. Fancier options use nanotechnology and ceramics to completely prevent fog.

I might recommend adding a film before you try swapping out your entire mirror. There’s a much better chance that the film will fit better, look better, and work better than swapping out the full mechanism. However, the choice is ultimately yours.

Use a Potato or Soap (Yes, Really)

For a more unique DIY solution, you can use a potato or bar soap to get good results. Yes, I had to try this for myself because I didn’t believe it, and it actually works.

For the potato method, cut a potato in half and rub the raw potato part against your mirrors.

Honey soap on towels

For the bar soap method, simply grab an unused bar of soap and rub it against the glass of your mirrors. You can also break off a piece of used soap to expose the unused insides.

Both of these options lower the surface tension of the glass, allowing moisture to simply roll away from the mirrors. These options stick around longer than the shaving cream option I explained earlier. Like shaving cream, these are very inexpensive fixes.

You’ll have to reapply them whenever you notice your windows fogging up again, but it should only happen every few weeks.

Use Fog-X

If you want to use the professional option, you should try out Fog-X. I mentioned earlier that Rain-X is a very bad idea for car mirrors, and this is the exception. Fog-X is part of Rain-X’s family, but it isn’t a water-repelling option. Fog-X’s only job is to keep fog away from your glass.

To apply it, spray the bottle directly on a microfiber towel. Wipe the towel across your mirrors slowly. Wait a few seconds then use the dry, clean side of the microfiber towel to pass over the mirror and dry the excess product.

Rain-X Interior Glass Anti-Fog – 12 fl. oz.

Rain-X 630046 Interior Glass Anti-Fog - 12 fl. oz.
Rain-X Interior Glass Anti-Fog Spray

Also, read the label carefully before applying it. Rain-X has a few different glass treatment products, and a lot of them are only for interior use. You need to make sure you’re using the option that can be used on exterior glass.

Using an interior fog repellent will wear away almost instantly once you put it on your outside mirrors. You need something more robust and able to handle the elements.

Conclusion

Now you know more about fog, why it happens, and how to prevent it on your outside mirrors. If this guide was helpful, consider checking out more of my guides on my site. Also, drop a comment below and let me know. As always, check out my list of helpful car products that might make your life a little easier.

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Ernest Martynyuk

An automotive enthusiast who's been tinkering with vehicles since I was 15-years old. Repairing automotive electronics has been my main job for over a decade now and have a passion for everything technical regarding cars.

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