Insurance is a gamble. You're betting against the insurance company that you'll collect. They're betting against you that you won't collect. Either way, you'll lose. They have your money up front. You're paying for a repair that you may never need. Keep your money and use it for what YOU need it for. The insurance normally does not cover wear and tear parts (brake linings, spark plugs, oil changes, maybe not even seals and gaskets). Also, if you fail to maintain the car, you'll be denied coverage.
I have NEVER bought extended warranties on anything I've purchased. I'd never had collected (time proven). Take the money you'd spend on extended warranties for your car, TV, microwave oven, DVD player, computer, printer, fax machine, mp3 player and all the other stuff and put it in a bank. You'll be dollars ahead.