Should you rustproof your vehicle?

Check any older car that has been driven in the rust belt in winter months, and you will find some rust on body panels or chassis components underneath. The major factor that causes the rust is the road salt. It's used to melt the ice and snow during winter. Rust ruins not only body panels, but mechanical parts as well. Rotten frames and subframes, broken coil springs, leaking power steering lines are just a few examples.

Since about 2010, car makers use better metals and coatings, but no car is immune to rust. The deadly mix of moisture and salt accumulates in hidden areas and destroys metal parts and body panels slowly from the inside out.

Many car dealers and independent auto repair shops offer different types of rustproofing that is intended to slow down the corrosion process. Typically, they spray a gel-like oil/wax mix or an oily solution on the undercarriage and inside the body panels to repel moisture. Some shops offer undercoating, which is spraying the underneath of the car with a black tar-like substance that hardens when it dries. Should you rust proof your vehicle?

Rust proofing a new car is worth considering if:
- you plan on keeping your car for more than 5-6 years,
- it will be driven in winter when salt is used on the roads, and
- the vehicle is not sufficiently protected from factory.
What do we mean when we say "protected?" First, while the typical rust perforation warranty is 5 years, some manufacturers offer longer warranties. Audi, for example, offers a 12-year limited warranty against corrosion perforation in the US and Canada, according to their website. Many BMW models also carry a 12-year unlimited mileage rust perforation warranty. In general, BMW, Volkswagen, Volvo and Audi have a good reputation for rust resistance.

Second, many modern cars and SUVs have plastic shields protecting rust-prone areas such as lower portions of the doors, wheel wells and underbody. Check, for example, this Toyota RAV4 in the photo. A large portion of the bottom of this vehicle is covered by plastic panels. Plastic trim pieces also cover the edges of the fenders and lower portions of the doors, protecting them from sand and salt thrown from the wheels. There are still some metal parts underneath that can rust, but rust proofing such a vehicle will not give you as much value for the money, since it's already well protected.

On the other hand, check out this truck in the next photo; it has no protection at all. Rust proofing a vehicle like this will pay off if you want to keep it for many years and plan on driving it through salty winter roads.

Of course, when buying a new car, if the dealer's rustproofing seems too expensive, you always have an option to rust proof at an independent shop.

How much does it cost to rust proof your car? Doing rust proofing in an independent shop costs from $89 to $200. We heard from a few car owners that dealers pressured them into buying rustproofing, mentioning that the factory warranty will be void if it's not done. As far as we know, this is not true. If you want to confirm, you can always call the car manufacturer customer service number.

When rust proofing an older car is beneficial: To answer that, you need to know what's the current condition of your car, especially underneath. If you just bought a used car, it might have already been rust proofed. When you take your vehicle for an oil change, ask a mechanic to look underneath - are there any rust spots that need to be sprayed? Of course, rustproofing doesn't fix rust, it only slows it down, so it won't help if the car is already badly rusted, like the one in the photo. If the car looks like this on the outside, many important undercarriage components as well as brake lines and fuel lines are probably in bad shape too. It might not even be safe to drive - it's time to look for another car.
if your car is still in good shape and you plan on driving it through a few more winters somewhere in rust belt states or Canada, rustproofing will help protect it. Rustproofing not only extends the life of the car, but also helps preserve the resale value of the car.

What's the best way to rust proof a car? There are several types of rustproofing products, and many disagree which product is better. To see different perspectives, we spoke to two car enthusiasts. One said that he gets his 8-year old truck (in the photo) oil sprayed every other year, because the liquid oil-type product penetrates better into all nooks and crannies.
Another said that he hasn't sprayed his car yet, because it's only three years old. He will get it done with the gel-like oil/wax spray later, but only if he notices any signs of rust.

In our opinion, a tar-like undercoating works well on open areas that get splashed on by water and sand from under the wheels. The gel-like oil/wax non-dripping spray is ideal to cover most of the undercarriage, including inside the fenders, strut towers, and the engine bay metal, although it will be washed off in the areas around the wheels. It also covers cracks in the undercoating well. The oil-like spray penetrates well inside the frame, rocker panels, load-bearing beams, inside the doors and other hidden areas. Of course, the oily spray will drip, and it can cause some rubber and plastic parts to swell up.

Some rustproofing shops drill holes in a few places in a car to be able to spray some body panels from the inside. We prefer rust proofing without drilling holes, as over time, the edges of the holes tend to rust.

How often should you rust proof your vehicle? Doing it every year is probably too much. We noticed that cars that are sprayed every year tend to have a noticeable oil smell inside. Modern cars with complex transmissions and small turbocharged engines are unlikely to last more than 18-20 years anyway. We would recommend having it done once and then having the vehicle checked every year before winter and re-spraying areas that show signs of corrosion.

Should you wash your car before rust proofing? Yes, and give it some time to dry. It's a good idea to run the vehicle through the car wash that washes underneath every Spring, to wash off all the salt. The best time to rust proof is in the Fall.

What about electronic rust-protection modules? It's a simple electric module that is powered by a car battery and is connected to two metal bars attached to the car body. We haven't seen too many old cars with such a module to judge their effectiveness. Opinions about them online and on Youtube are mixed. If you want to try, we found rust protection module kits sold on eBay for $90-$150. It's easy to install.