Depends who's offering the contract and the terms.
A manufacture warranty is not bad.
But many of the warrenties ars thru private companies or the selling used car lot.
They range form no different from buying a new vehicle, an effort to a point, to an all out rip-off.
Look at the following:
Who stands behind the warrenty.
What is covered. While it could be said the engine is covered, it can be a huge difference between power train and internal engine and trans. Internal engine may be limited to parts like pistons, rings, bearings, rods, valves, cam, rocker arms, chain, oil pump, crank. Power train might cover items like cracked plastic intake, oil leaking out of engine, sensors, fuel injector, alternator. More often the smaller items fail like sensors, belt drives, fuel pumps, small gasket lesks. What about stearing, brakes, suspension, accesries.
What is not covered. See what they concider wear and tear items, abuse, comercial use, modifying.
Who can repair the vehicle. The orignal new car dealer have a great advantage of having replacement and test parts, factory repair tools, repair information, latest tec bulletins, and most likely experiance with the same problem. The problem with the deals where you have to bring it back to the same place you bought it from is your at their mercy. You could wait weeks befor it's in the shop. They may not be able to repair it correctly and you cant go elcewhere.
The deductable. Sometime the repair would cost less then the deductable. I remember one time someone paid the deduct, mabe $200 to get a $70 tire replacement. Many times the repair cost just over the deductable on a fair price.
What parts will they use to make the repair? A factory warrenty will use new factory parts or factory remanufactured assemblies which tend to be top notch. Some warrenties don't specify. Most offten it is the cheapest replacement parts or rebuilder. In many cases they will use salvage car parts. The milage and history of the parts are questionable. The salvage yard will always say (or lie) it is from a low mileage car. Sometimes it's from an older or diferent vehicle. Or the parts were thru a crash, fire, flood, etc.
Do you have to wait to get reinbursed or do they pay the shop directly. Some shops don't want to deal with these warrenty co. just like some EC don't want to be involved with home warrenties. They don't want to wait to get paid, risk no payment after waiting, deal with long phone calls on hold, paperwork, or have the warrenty company dictate how much they will pay.
Do you get a loaner vehicle or rental credit?
The worst story I remember is a guy with spun rod bearings. He paid to have it towed in. He paid the $250 deductable. Then he was told the warrenty company wanted to see the inside of his engine. Then was told he needed to front the cost to remove and partial disassemble the engine, and would be reinbursed by the warrenty co. Paid another $500. Warrenty company looked at the parts and denied the claim as customer abuse. Put all the engine parts in the trunk and they towed it away to a customer pay shop. I'm guessing he put out around $2,000 for the warrenty, tows, and disassembly. At the time that would have been close to the amount for a shop to put in a rebuilt engine. My guess is the next shop did not give hive a good price to finish it.
The one problem I seen with a factory warrenty is they don't want to aprove some claims just after you made the purchase. The reason is, it should have been inspected and problems repaird by the dealer before the sale.