Believe it or not, but treating your car to the best underseal is one of the best things you can do to ensure its safety. Keeping a car shiny from the best ways of paint protection is all well and good, but the underside doesn’t have a nice coat of paint to protect it from the elements.
No matter how well a coating of car wax works on the bodywork, it’s underneath where you’ll find the nasties. Take a peek underneath any car a few decades ago, and you’ll either see the worrying signs of rust forming or a thick black coating of primitive underseal, often made of bitumen.
Older cars have their fans for various reasons, but rust protection was never one of them, and steps need to be taken to avoid expensive damage. Thankfully, modern underseal is affordable and easy to apply, and we’ve been hard at work finding the best examples on sale.
The best underseal at a glance:
Editor’s pick: Bilt Hamber Dynax UC – Buy from Amazon.
Best for after a refurb: Liqui Moly Bitumen Underbody Protection – Buy from Amazon.
Best value rust protection: Hammerite Underbody Seal – Buy from Amazon.
If you do happen to own an older car, or you just want a little more protection than paint sealant. Aftermarket underseal (or underbody protection) is a hugely effective way to keep your car safe from the elements.
The best underseal
Editor’s pick
And if you're worried about rust (i.e. you own an old British sports car), Bilt Hamber also sells a version (called Dynax-S50) for protecting internal cavities that pose a rust threat, like chassis rails.
Pros
- Very easy to apply
- Provides ample protection
Cons
- Isn't the answer to protecting internal cavities
Best value rust protection
Pros
- Comes in large tin
- Can easily be applied with a paintbrush
Cons
- Not as straightforward as an aerosol
Best for after a refurb
Pros
- Will treat your underside very well
- Clever tech
Cons
- Existing rust needs to be removed first
Best for a number of applications
It can be used on clean or previously rusted metals and is a solid choice if you don't want the underside of your car coated in a black layer. If you want to preserve a rusted look on an old vehicle or object (i.e. like a Rat Rod project), this is the ideal spray to protect the metal.
Pros
- Ideal for a number of surfaces
- Easy to apply
Cons
- Others offer better protection
Best underseal bundle
This three-pack set is the best value, in our opinion. It's a shame you only get 500ml bottles to play with, but nevertheless, each use should provide ample protection to the underside of your car. And the great thing is that it can be applied to other objects and surfaces as well. Be aware that it's not a clear coat and that the aerosol sprays out black!
Pros
- Comes in a pack of three
- OEM approved for both classic and modern cars
Cons
- The bottles are only 500ml each
How does underseal work?
As well as wheels and subsequent need for wheel sealant, the underside of your car is subjected to a lot of wear and tear. From stones flying underneath it, chipping away at coatings to salt, water and other contaminants. It can all quickly become a breeding ground for rust. As the underbody is crucial to your car’s structural rigidity, failing to stop rust can cost you a fortune.
Important structural parts of a car will be inspected during an MOT. Rust can see an immediate MOT failure, so it does make sense to check cars for rust and prevent it from forming. Underseal works as a thick layer of protection. It ensures that rocks and stones bounce off and that salt and other debris doesn’t begin rusting your car. The whole process is quite a bit more thorough than, say, applying black trim restorer.
Happily, however, we’re far from the days where cars barely lasted a decade before they were ready for the scrapyard. Factory underseal and rust protection has improved massively in recent times. However, keeping such things in good running order still takes effort, which is why underseal is a worthwhile purchase. Things like tyre dressings are more of a treat-yourself item in comparison. And even if you are running a classic in all weather, it’s a no-brainer if you want to keep your car on the road.
Ryan Gilmore is the Deputy Autos and Tools Editor for Parkers, specialising in car cleaning and hand tools. A veteran car cleaner; if it details, waxes or washes he’ll be on hand to make sure it’s worth your money.
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