We have a 2014 Toyota Corolla with a little under 30,000 miles. A few months ago some road debris resulted in a punctured tire (rear passenger side). We had the tire fixed, but found out that they plugged it and didn't actually patch it like we thought. Since it leaks air when it gets really cold, we went to another shop to see if they could replace the plug with a patch, and said we should replace the entire tire.
The mechanic insists that we only need to replace the one tire, saying its only the rear and that the other tire has minimal wear. I know you should normally change tires in 4s or at least in 2s on the same axle. The tires are primacy MXV4, which has a 60k miles warranty.
At 30k miles, I assume that the tires cannot really be like new, even though the car is just for commuting. I am also concerned about how this impacts syncing up with future tires changes for the other tires. I would rather change both and keep the rear driver side as a full spare rather then rely on the donut. I was willing to pay for more tires+service, so I assume if the mechanic is trying to talk me out of it, he has a good reason (why would he not want to make more money?)
Any validity to his point of view? Or should I insist on giving him more money?
Edit: The replacement tire is the same type/size as the stock tires on the other 3.