Yep the battery drain and bluetooth issues on Oreo are a PITA.
I flashed Nougat back on my Pixel XL and happy days again. I'll upgrade to Oreo once those two issues have been fixed.
How did you flash Nougat back on? Where did you get the file(s) for it? I'd be worried of invalidating my warranty.
TheOracle, have you received your replacement Pixel XL yet? I assume the Bluetooth/car issue is going to be there anyway. I tried the gf's Pixel on my car Bluetooth and it didn't work either. I just wonder is there anything I could do with Google/CPW saying i haven't had my Pixel for a year and it's clearly not performing as it should?