Car club members, especially in northern climates, will often have at least two cars: their pride and joy and their winter beater.  Whether you drive a winter beater or a show car, your car will benefit from being undercoated.  Undercoating comes in a variety of forms and some forms protect better than others.  Generally, any undercoating is better than none.  The only cars not recommended for undercoating are show cars that are trailered to judging events and are never exposed to the weather.

Eventually, road salt catches up with winter-driven cars and no amount of body work can save them.  For these winter beaters, a good oil spray (really any oil spray) really helps to squeeze a few more years of cheap service from these cars.  Without having done a cost-benefit analysis, we will go out on a limb to say that the cost of even the cheapest annual undercoating job will pay back with an extra year of service.

For your pride and joy, a good oil spray will also help to protect it from the elements, even if you don't drive it on salted roads.  Even if you avoid driving your car when it's raining, there is a potential for corrosion to occur just from the moisture in the air.  Even if you only do a $150 undercoating job once in your car's lifetime, that investment will most certainly save you much more in rust repair jobs years down the road.

Professionally applied undercoating usually comes with some sort of warranty.  The warranty is there to protect the shop from you making a claim.  Just think about it.  If the warranty was there to protect you, there wouldn't be a warranty with all its exclusions and they would just take care of you because you had the receipt.  When you hire someone to undercoat your car, find out what they are putting on and how they are doing it.  Remember buy the undercoating, don't buy the warranty!

Some things to consider: