As others have said, it depends on mostly on good maintenance. It is not unheard of for transport trucks to roll over 1 million miles.
However, as a general rule of thumb, diesels engines last long than gasoline engines as the fuel acts as a lubricating agent.
However, depending on climate, your car will likely rust out LONG before the engine dies. Ask for evidence of yearly oil spray application (esp. Krown).
Other than that, make sure the title is clean (no flood damage, ins write offs, etc)
One thing to watch for is the periodic expensive maintenance. For example, VW diesels have expensive maintenance every 160 000 km. When I was looking at used, there were a lot of cars for sale at 160k, 320k and 480k km. They either didn't want to spend the money on the repairs, OR their mechanic found a lot of repairs needed during that service.
I don't know about expensive maintenance for other cars though.