The first tip about purchasing an auto warranty is that you never purchase is warranty unless it is truly an auto warranty and not some plan where you get minimal warranty coverage.  Both new auto warranties and used car warranties should be provided upon purchase of the vehicle, or not at all.  Sometimes even if these warranties are included, you might need to pay for transfer to your own name.
The only auto warranty that you should purchase is the aftermarket warranty.  It is advisable that you never purchase a warranty from the car dealer from whom you bought the car.  This is simply because all car dealers mark up their prices by as much as thirty percent and over.  Also, you must never buy an aftermarket auto warranty that is included within the final price of a car that you purchase under loan agreement.  This is because all loan purchases will carry an interest charge that would be spread over the total period of payment – that means that if your warranty was included in that price that you would be paying interest on it for years to come.  This could amount in hundreds of dollars unnecessarily spent on a warranty coverage that is worth less than twenty five percent of that.