I picked up 4 OEM "Ecco" Jeep wheels with mounted tires for $150.
Tires are from 2009. (Cooper Discover) 2 tires at 3/32 are shot.
The other two have 7/32 and 9/32. 9/32 seems like a keeper. 7/32 seems ok.
Tread Depth Gauge $3


I only needed 2 more tires, but found a set of 4 used tires for $120.
3 tires (Wrangler RT/S) are from 2008, and have tread of 10/32, 10/32, and 9/32.
The 4th tire (Wrangler AT/S) is a never used spare that is now 12 years old. It has a chunkier 15/32 tread. No dry rot.

Should I not use the 15/32 tire along with three other 10/32 tires b/c of the significant tread difference?
Would you not install that 15/32 spare tire b/c it's 12 years old? **

For now, I think I will dismount 3 of the Ecco tires (only keep the best one 9/32) and install the 10/32 10/32 and 9/32 tires. (And save the 15/32 as a spare?)
This way, all tread is 9/32 or 10/32. Decent without large variation. I heard that different sized tires cause issues. I do feel bad about tossing out the 7/32, as it's far from done.

What would you do?

 

I think your overthinking this.... surprise, sounds like you have a plan.. 4 tires on 4 wheels

 

Most tire places won't mount tires over 10 years old. If there is no dry rot though, I'd run it.

 

You've got a good idea. Just go with that