Should I Undercoat My New Car?

by Tom King
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If you are negotiating to buy a new car, one thing you can count on hearing about is “undercoating.” Dealers love to add optional undercoating at a substantial price to the cost of a new vehicle, claiming that it will make the car quiet and protect your chassis from rust and corrosion—which will make your car last longer. So, is undercoating worth the cost?

Coatings Already on the Car

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New cars come from the factory already coated underneath with a variety of coatings that are designed to protect the chassis from such things as rust, salt and oil. The dealer’s add-on undercoating is a black substance that looks like tar which is sprayed underneath. Whatever the dealer tells you, undercoating is not primarily a rust preventative. Undercoating is designed to deaden road noise and to make the interior quieter, not to protect from rust.

Hazards of Undercoating

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Undercoating may give you a false sense of security with regards to your under-carriage’s resistance to rust and salt corrosion. The undercoating material is too thick to get into tiny crevices where moisture can collect. Undercoating can even clog up drain holes in the frame that are designed to drain water from areas where it might collect. While undercoating will prevent some rust, it must be applied when the car is new and the chassis is perfectly clean. Undercoating poorly applied can trap rust-causing and corrosive substances against the metal of your car and cause corrosion beneath the coating where you can’t see it.

Worth the Expense?

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Today’s cars are well-made, and a variety of techniques and engineering improvements have made them more resistant to rust and corrosion. As a result, severe rust on a car is very rare. Since most vehicles today come with five- to seven-year or 100,000-mile warranties, you probably don’t need undercoating, and as pointed out previously, undercoating can actually create more damage. Unless you are in an area where a lot of salt is used to clear the roads of ice and snow, undercoating is probably not necessary and can add significantly to the cost of your new car.

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