Fleet maintenance, 173 cars/trucks/vans that I get to keep on the road.
Change the filter at 12,500 miles, change the oil & filter at 25,000. When you use it that way the amsoil is cheaper. IDK if I would have picked 20W50, but that choice was above my pay grade. Some of the vehicles have over 150k on them doing this, and we average one internal engine problem per year. Two were sludging that only required cleaning the oil pickup (V8), one was a seized roller in the cam follower (V10 at 28k, probably a defect really), all 3 were in ford OHC engine trucks.
It's not that bad, considering all of them are driven by people who know they don't have to pay to fix them. They all get beat on pretty bad.