Synthetic oil use on flat tappet cam after break in

Parents bought a Ford Tempo back in 1987 just as I got out of the military. After break-in we switched to Mobil1 and changed at 5000 mile intervals. Car run great until 175,000 miles, when the oil pump quit. Before Dad could get off I-75 it started to clatter. I went investigating and found the entire engine full of the nastiest sludge, I couldn’t have imagined. By that point the car had paid its dues and got recycled. It was replaced with a Purple Gray Neon.
I have shy away from using Mobil1 in anything since but, I would expect by now that formulations, no longer be the same.