I know this is older thread and doesn’t get much attention but with the Cadillac EV the original factory warranty is 8 years and 100k miles on the motor and battery.
Not sure how much value you would get with buying “Extended Warranty”.
Putting $3k in S&P index fund, same amount in any quality growth stock like Nvidia, SpaceX or even GM will be worth at least $4k or more in 3 years. If you have an issue just sell and if you don’t have an issue you have the equity to keep or liquidate and use for down payment on a new vehicle.
Just buying $3k in GM stock 3 years ago would be worth over $4600 today and GM is not even a good growth stock.