I got a flat tire on front passenger side yesterday and I went to Costco tire center just to get a new tire quick. But the salesman told me that I must replace all four tires at once b/c G37x is all AWD.

His explanation of course is that new tire rotates slower than those older worn tires and this rotation speed difference will ruin the AWD transmission later on. By google search I found some AWD cars seem to be indeed very stringent on tire size difference, but some are not so sensitive. I looked at G37x manual and didn't find any warning of such.

I finally went to the Infiniti dealer and they just replaced the bad tire with an identical model (Yokohoma 225/55R17 97V). They told me that the other three tires are relatively new (~10k miles) so putting on a single new tire is fine.

I just want to make sure with you guys what the dealer did is fine. I hate to replace all four tires and throw away three semi-new tires. But I don't want to risk ruining my transmission either...

 

If they were summer tires the one you replaced would be a fair amount worn vs. those All Season Yokos, you should be fine. I'd put the new tire along w/ the other front tire in back since the rears wear faster. That way the tires with the least wear would now be in back, and would eventually get closer in diameter to your current (more worn) back tires. Hope that makes sense.

 

Thanks! Yes they did a tire rotation which was due anyway based on the maintenance schedule anyway. So the new tire is in the back. I learned sth new today about AWD. Never thought this could be the case.

By the way, I think this dealer (Wexford/Pittsburgh, PA) was pretty reasonably priced. One new tire, oil/filter change plus tire rotation was $248 including tax and a free car wash/quick detailing. The cheapest tire I found at Costco is $160.

 

Yeah, just beware of those free dealer washes, can be pretty good at scratching & swirling the clear coat, at least in my experience. Glad you got it taken care of