if new you get a lot of warranty 4 year 50,000 mile bumper to bumper and 6 year 70,000 mile powertrain if you are going to keep the car beyond this timeframe an extended warranty is not a bad idea.....never buy dealer warranties only buy the manufacturers it will barely be more expensive (probably 1 or 2 hundred dollars more) but is a factory warranty good at any GM dealer nationwide (life happens...what if you move, the dealer warranty wont take care of you then) the factory warranty comes with roadside assistance (roadside is part of powertrain warranty extend that and you extend roadside) it can be canceled for a prorated refund and it can be added any time during your cars original warranty period (let it expire and you're out of luck)
one caveat is affordability as i said before you can extend the warranty any time while its active but it will be for the whole amount out of pocket....if you know for a fact that you want it at time of purchase get it then it will only add a few dollars to your payment
better yet have your dealer do a cost analysis for you and compare a 6 year purchase vs a 3 year lease plus 3 year purchase....often times you can save alot of money this way because lease incentives might actually be better than sale incentives and you still end up owning the car.....this method also plays into your hands because you can opt out of the extended warranty during the lease but get it at lease end when you buy the car.
don't be afraid to make the dealer jump through your hoops...right now you're jumping through theirs with their in house warranty offer.....MAKE them show you a lease and a buy and MAKE them show you a short term buy at lease end add up all your payments for both and go with the cheaper option
also as an interesting long term benefit if the lease+buy is cheaper at the end of 6 years your credit will show two satisfied loans instead of one very minor but a benefit nonetheless AND you may trigger more private offers from GM...a private offer is GM's customer retention program, basically in a couple years you will start getting post cards from GM saying dear valued customer you have earned $1000 off your next GM car for having purchased with us now you might get a different one for leasing too
and if you really want to get crazy get a GM card
now in year 6 when you're ready for a new car...you have whatever deal that is on the table...you can then ask you dealer to check the manifest list for any unredeemed private offers (if they haven't done this already for you, i was always able to find between $750 and $2500 extra dollars for about a third of our customers who purchased GM in the past) and whatever you earned on the card
who knows this might cover the extended Warranty on the next car