Undercoating: do or don’t?

One question everybody’s been asking me this season is whether or not to undercoat their vehicles. It’s an oldie but a goodie as far as topics, so here goes:


My thoughts on undercoating.


In theory, undercoating is a really good idea. Rust kills any car in the end, unless you’re somewhere in California and wash your undercarriage religiously. For the rest of us, snow, slush, and salted roads are constant worries. Undercoating is supposed to solve the problem by coating the bottom of your vehicle in a resistant material that doesn’t rust. That’s why so many Northerners swear by it: it’s supposed to be this magic sheet of armor against slush and salt rust.


Depending on your car and where you live, it might actually be a good idea. A lot of older vehicles used steel in the undercarriage, which can rust quickly. And people in extra snowy places do have a legitimate worry about rust from the roads. For a couple hundred dollars, getting protection against the elements looks like a good investment.


On the other hand, it’s damned near impossible to get undercoating completely right. Most of the time, the person doing the job misses a small spot, or accidentally ends up sealing a pocket of moisture to the bottom of your car. So, more often than not, undercoating does more harm than good. Plus, most new cars don’t need any additional coating. And if you end up having one added, you’ll probably end up voiding your warranty at the same time, even though you and I both know that most car warranties aren’t worth the paper they’re printed on.

car coating

Here’s what I’d say to anyone thinking about having it done. If you have a new car, within the last 10 years or so, don’t worry about it. Seriously. Even if you live somewhere cold, new cars are almost all aluminum, and they’re coated out of the factory with some pretty sturdy materials that I don’t really see rusting too much. Save your money and just do a good job washing the undercarriage, and don’t keep a snowy or slushy car in warm garage, because you’re just asking for trouble.


If you have an older car that might be at risk of rusting out, or a newer car in a super rust-prone part of the country, you can think about undercoating. But before you do, make sure you find somebody who’s incredibly good at it, and make sure your undercarriage is absolutely spotless with no rust at all before you take the plunge.
But for most of us, it’s an unnecessary step that’s not worth the risk.