A, the 2-stroke smokers! As long as you had a good supply of rod slipper bushings for the wrist pin, you were set. DD recommended straight SAE 40 wt oil in summer and 30 in winter. Why? To keep the oil from pumping out the slipper bushings too fast!
In the Mobil Oil Industrial Territory, we had the Iron Mines - all the haul trucks in those days ran DD 16V149's, even though they broke down a lot. Asked why, the mine supe told us they were documented lowest cost per ton of ore, even despite all the breakdowns and loss of productivity.
That'll tell ya how cheap those motors were compared to Cat & Cummins!
You could hear a DD a mile away with their twice as often power stroke - 1800 rpm sounded like 3600 rpm!