Yeah, they are all older but still run well. Although I haven’t taken apart any of these engines to measure clearances, etc. they do not use oil between changes and the engines sound smooth without clattering or knocking sounds. I am sure some wear has occurred but cannot tell. The Ford has many more miles than the Chevy which has around 110k. I have had that once since it was new and have always been a stickler about oil changes and other routine maintenance. I know people who have gone up a grade or two in viscosity to maintain oil pressure and prolong the life of really worn engines but these still have like new oil pressure on the gage.
Some engines, especially the valve trains, are picky about oil viscosity. For example, using too thick of an oil in the 3 cyl Geo Metro I have, especially the cold/startup viscosity, will result in the lifters overpumping and burned exhaust valves rather quickly. Most run a 0W or 5W oil in these little engines. A 10W is bad news unless you live in a warm climate and mainly drive on long trips where startup wear becomes minimal as a percentage of miles traveled. I know other engines, especially those with some type of variable valve timing, are not forgiving to using other than the specified oil weight.