The markets for EVs and gas cars are fairly established, so your personal choice to keep fixing your car vs selling it to someone else who will fix it instead doesn't have a net change on the environment. Nor does your choice to buy a new car or a used car.

The only thing that matters, really, is whether you are personally supporting the oil market or the electric market, how much, whether electric generation in your area has a good mix of green sources, and your support for political willingness to embrace policy that identifies and prices-in the side-effects on the environment, such as eliminating subsidies for oil companies. It all boils down to your willingness to put your money where your beliefs are, which for some people is very hard to do, for some people is not very hard to do, and for some people the environment just doesn't factor into their decision making at all. Tragedy of the commons, or will enough people actually care? Those who have the means and the awareness, definitely should.