Got FR series engines with way over 1000 hrs on them, some with over 2000 hrs al running fine
The only ones I have has problems with were ones that the owner serviced and did the air filer clamp up too tight which allowed dust to be sucked into the engine wearing the rings .
So 2 have been re-ringed & now they have Donaldson filters on them, both are running fine , both of these were baggers
Four have needed a head repair because the single clamp bolt on the rocker housing came loose so I now check it is tight every service .
Car oils have different formulations to mower oils, but 20w 50 will not cause an engine failure the one caveat on that is to change it on the final mow for the season, every season .
The reason for this is mower oils have more corrosion inhibitors, water dispersants & anti-sludging agents than car oils because the engine sits around for 3 to 7 months each year depending upon how long the off season is in your region.
And FWIW Kawakasi Australia specify 10w40 and market their own branded 10w40
Got lots of customers who run the same oil as their car uses so they only have one oil in their shed and it stays fresh
An old addage from the vintage motorcycling movement
The best oil is what you have just drained out and the more often it is drained the better it becomes