If you make the sump big enough you can extend the oil change that much longer. On stationary engines such as used in the oil industry, the sump hols about 1 BARREL of oil for a 700 HP engine and there are a number of filters attached to the engines. So even when these engines run continuously they only have one oil change per year. That coincides with other maintenance activities. The oil is normally analyzed every month to check it’s quality.
A Class 8 highway truck sits high off the ground and can have a very large oil sump since it’s only a small part of the overall weight. For a 500 HP truck engine you can make the sump large enough to go 100,000 miles between changes. These engines have several filters and truckers regularly test the oil, usually every 30 days. Continuous driving is also very easy on oil, which normally is 15W40 Heavy Duty diesel oil.
On a passenger car there is little room and ground clearance, so a smaller sump is used. It’s a compromise between avoiding sticker shock when the owner goes for an oil change and having a long enough interval between changes.
The large marine engine shown has a separate large oil system and oil is purified by centrifuges and filters. The oil might be changed once a year but would be regularly tested.
I spect that there Marine engine wouldnt have any trouble consuming its own waste oil.one thing about diesel engines ,you should never overfill them to the point where they can start ingesting their own oil ,they will literally run off and they are hard to stop,bubbas Mack ate a turbo and starting running away from the governors ,He had a hard time killing it in high gear,I had a Lister -Petter small diesel run off one time because I overfilled it with oil,Boss wouldnt listen and get me the book for it ,told Me to service it anyway,I didnt know any better and filled the crankcase cleanup on it ,it burped a couple times and started screaming ,my nutty ass helper stuck his head in the enclosure with it(despite my protests ) and turned the throttle off on it ,which I dont think made any difference it had burnt the excess oil by then (He would have had a rude awakening if the engine had grenaded ) That stupid punk finally went on to become our county Sheriff and He has actually made a fine Sheriff. Some of the old aviation diesels where hard to shut off because they would keep running on crankcase fumes ,I guess thats why most Diesels up until recently didnt have PVC systems.
When the body of my car finally rusts out, I plan to use the motor in either a street legal dune buggy or a rear-engine trike with a raked out front end.
I’ve noticed the same thing when I use synthetic motorcycle oil in my 2003 Nighthawk 750. When I use conventional motorcycle oil, it burns oil. When I use synthetic oil, it doesn’t burn oil, or burns so little that I don’t notice.
My only working theory is that, because it’s an air/oil cooled engine, it benefits from having a type of oil that can better withstand high temperatures.
I’ll add to the theory: synth oil burns off the cylinder walls more slowly, so the rings etc. don’t have to replenish the (extremely thin) oil film as much.
I have the exact opposite experience in my Intruder. I put in synthetic oil to quiet the gear box and it drank it up like sailor in port for the first time in a year. I literally had so much consumption it was suffering effects of low level after a 100 mile round trip commute. Kept it topped off for a week but got tired of it and went back to conventional oil and it immediately returned to not using any oil. I learned to live with the gear box noise after that…