For what it's worth, the last company I worked at bought auction vehicles, cars, vans etc and kept them till the tranny goes out most had near or over 300K and they used Mobil 1 and changed oil every 20K, All these vehicles ran beautifully and they did oil analysis on them....accidents and tranny problems is what killed them.
On a personal note in my personal commuter car a 2005 Scion Xa, mostly highway miles I change the Mobil 1 every 10K
Now on my '68,'69,'70 VW's I change the oil every 3K with dinosaur oil, but they have no oil filters, and synthetic makes em leak too much