The biggest advantage of undercoating your vehicle is that it protects the underside from rust and damage. The best undercoating products also protect electrical and mechanical parts from moisture, which can significantly reduce vehicle breakdowns and repair costs. The disadvantages of having the service done include the cost and the added weight.
Having a car undercoated is an expensive service that can add a hefty sum to the final price tag of a vehicle, which could pose a problem for car buyers on a limited budget. The added weight of the undercoating may seem insignificant on the surface, but it has a slight effect on the fuel economy of the car.
Car professionals do not recommend undercoating a brand new car because it still contains factory rustproofing. Most modern cars do not show any rust until about five years of constant use, so the best time to undercoat a car is when it is more than a few years old. If your car is on a standard 3-year lease, or if you plan to trade it in after a few years, it doesn't make sense to undercoat your vehicle.
If professionally done undercoating is too expensive, there are alternatives that allow a car owner to save money, such as DIY rustproofing kits sold by car supply stores.