I have always had good tire experiences with Costco. No one there works on any sort of commission. They have never tried to up-sell me and in fact the last three times in there I had to ask about more expensive tires. They do have some internal controls. After my 97 Explorer ran through its factory Firestones I put on 4 of their Kirkland Sig. brand tires. I put about 20,000 miles on them and then the whole Firestone recall/fiasco happened. I still had the original Firestone spare and was about to go on a 500 mile road trip so I went in to get the spare changed out and the others rotated and balanced. The guy was sorry but he couldn't sell me another KS tire. He also couldn't rotate or work on my existing tires. Ford had issued their approved tire replacements for the Firestones and the private labels weren't on the list. Costco legal decided that they weren't putting anything on that wasn't on Ford's list. So, he took my 4 KS tires back and credited me full value. I got four new Bridgestones for like $20 total.

You'll note that they don't do their private KS tire label anymore as a direct result of the Firestone recall. They also have this disclaimer on their website: For your safety, Costco only installs authorized tire fitments. The final decision to install a tire will be made by the Costco tire center manager or supervisor.

One final note, on my 300TDT they sold me 205/60s twice now (I got a few spares recently) and those are not on their fitment guide.

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1987 300TD 231,000
#22, afterglow, plastic fan, euro lights, alternator upgrade, cluster housing update