2015 QX80 catalytic converters

Hello -
I just purchased this from a law enforcement guy whose FIL owns the dealership. It has 155k miles but the selling point was the binder he gave me filled with every service record. Plus he gave me a good deal.


After 1500 perfect highway miles I recently took it to dealership to have oil changed, tires rotated and have a 100-point analysis done on it. ALL WAS WELL.


I drove it off the lot. The next morning the MIL light comes on solid and took it back to the dealership. I'm now told the "codes indicate BOTH catalytic converters need to be replaced..."


After asking a few questions I'm told it's ok to drive 1000 miles on it (I had another upcoming trip). I call up a different dealership (that the previous owner had do all his service on it) and gave him the vin#. I ask him if maybe the sensor itself or whatever is signalling codes to the computer might be checked first before shoveling $8+k into the car. He talked around it a bit--focused his response on the full cost of diagnostics vs that cost being waived if I have the work done that the diagnostics suggest.


I drive mostly highway miles and although I don't know this car well yet it seems like it still drives the same but mileage gauge now sits consistently 16.9 vs 20+ that I was getting. (really...16,9? not 16.8 or 17.2) I drive with the mileage economy status window on that shows it fluctuating between 0 and 30 and it's at or very nearly 30 the entire time except when shifting gears (I'm in very flat country). While I'm not as concerned about mileage as I am about the care and maintenance, it is disconcerting.


Before buying I looked into QX80 issues and know that "things can happen" at this age and miles, etc. However, with all the catalytic converter drama the past few years, and this problem popping exactly right after it was serviced at a place new to me, I'm frustrated and a bit dubious.


Please share your thoughts and suggestions. Thx