If a petrol engine doesn't make it to 250,000 miles
somewhere between the initial engine designer and the owners / operators, something went very wrong.
For diesel engines, 300,000 miles MINIMUM.
was it a uber vehicle? I have seen more than a few uber vehicles with tons of miles on them, some of them are ran 24/7
I have not seen very many new ones with super high mileage yet but over the past 5 years or so I have seen some GM uber's with 400k on them
what some of these companies will do too is buy them new, run them 24/7 until the powertrain warranty is about to expire (60k typically) and then dump them while they still hold some value and never have to pay for anything but a couple oil changes.
Those kind of miles wouldn't bother me a bit. It means it was on the road and used vs sitting all the time. I've bought a handful of vehicles in the similar fashion. Most notable was a 2000 silverado 1500 4x4. Bought it 2 years old with 60k - construction superintendent truck. It was the best used vehicle I ever bought. Put 100k on it and didn't cost me a dime of failures and very basic maintenance
At least you know it was not sitting at the GMC dealership waiting for repairs. If was serviced regularly you should be good to go. It is generally the low mileage vehicles I am extremely suspicious about.