I have a genset ex emergency services that has an external oil tank because it is designed to run for a very long time
That gets the same Shelvsey 40 that I use in my total loss motorcycle engines.
IT has a side valve 9 hp Briggs
All of the old British motorcycles get non detergent oil unless I have upgraded the lube system to include an external oil filter.
All the modern engines get modern oil, mainly because I try to keep oil inventory to a minimum
So I have 44's of 20w50 detergent for the service vans
A 44 of sae 30 ( pink ) mower oil Detergent
A 44 of sae 10w40 mower oil detergent for all of the MODERN engines that use multigrades.
a 13 of sae 40 NON detergent for the motorcycles & generator.
And to add to the previous posts,
A lot of engines use centrifugal oil filters.
For British motorcycles it is inside the crankshaft and usually called a "Sludge Trap"
Honda fitted them as a stand alone on the small motorcycle engines till the 90's
A lot of the step throughs sold in Asia still run the centrifugal filters
Large stationary engines often have external centrifugal oil filters, particulalry those on large marine diesels