Convinced my buddy to change the oil in his 1974 Chevy Nova, and it “ruint” the engine. He hadn’t ever changed it.
They’ll run a long time without it, but the first time you put a full load of fresh detergent rich new in it it’s going to loosen up a lot of crud and circulate it around. Upon stopping the engine each time after, the particles still suspended in the system will become the resting surfaces for the bearings.
Always change it hot and at a reasonable interval. 380,000 on the 2011 Silverado with a gasoline engine at this point...