Do I really need four?

Here’s a link that may shed some light on the subject. Scroll down to #3 Vehicle Type. It talks about AWD vehicles and if you have to replace one tire, they shouldn’t vary more than 2/32” from another.

If it were me, I’d look for a good used tire with the same tread depth as the others. This works so long as you’re comfortable with an unknown tire. Les Schwab may be able to help you out.

Can I Replace Just One Tire on My Car? | Virginia Tire & Auto.