I got a flat, somewhere in the middle of Wisconsin. I got a misc. used tire from a local tire shop, to keep me on the interstate (spare’s a donut). The other tires are original, about 20k on them. Should I replace the used tire with a new one, or wait a year or so and replace them all?
I’d just go with a new one, since you do not have AWD on your car. If the used you bought is in as good a shape as the ones on your car, you could drive a year and replace them all. Your choice.
If the new one is not causing odd handling or undue noise I would replace the entire set of 4(next year). The odd handling will be more noticable in winter conditions or really wet ones.
Not to beat a dead horse, but will the spare tire well hold a full-sized spare? If so, I’d take a trip to the salvage yard, get a good rim, and put one of your original tires on that rim when you get the full set replaced. I’ve done that for every car I’ve ever purchased with those horrible donuts, and patted myself on the back whenever I had to use it. Luckily not often.