It's worth extending your warranty if your car isn't extremely reliable and you wouldn't necessarily be able to afford major repairs right now. If you buy a used car from a dealer, an extended warranty might be the right choice if you're not sure of the vehicle's reliability. If your car isn't the most reliable, you might be more comfortable buying an extended warranty than without it. If your car isn't very reliable and you're not in the financial position to risk paying for repairs or replacing it yourself, it might be worth paying a higher upfront cost for protection through an extended warranty.
But like the financing they offer, dealers tend to increase the cost of extended warranties to make a profit. For example, if a part of your car that is not covered by the warranty fails and damages a part that is covered, not all of the warranties will be amortized. If you're buying a used car or if the manufacturer's warranty has expired, it might be worth considering an extended warranty for the car. Extended warranties often have a lot of restrictions, such as what is covered and where the vehicle can be repaired.
While there is some overlap between car warranties and fault coverage, they are not exactly the same thing. This will depend on the manufacturer and you may have to meet certain requirements, such as requesting maintenance service for your car at one of their dealerships. When deciding whether it's worth extending your car warranty or not, you'll need to look closely at the terms of each policy. A native of New England, I have flown a wide variety of vehicles, from a Segway to an aircraft carrier.
In general, extended warranties are intended to prevent drivers from paying out of pocket for sudden repairs, since mechanical problems aren't covered by other types of car insurance.