It used to be the 3000 or 3 months but oil technology has improved cars also burn fuel more efficiently and fuel is cleaner. I now go 5000 miles or 5 months or 2 times a year. I even go once a year on my farm truck but it only gets 500 miles a year on it.
You have to remember when your car or truck is running, fuel vapor mixes with the oil vapor and it causes the oil to break down, that’s the purpose of the oil change, it also cleans the engine. if you don’t change the oil it gets fuel soaked, and when you shut off the engine that layer of oil that is touching the metal in the engine it stick to it, eventually growing a thick layer of sludge.
I know oil changes seem like a pain in the a## but so is an expensive engine repair, like stuck rings, you can’t clean those easily and you might as well put an engine in. So you decide oil change or engine change.
Happy motoring diesel engine oil changes 5-7000 but, again new oil technology. And for those who know a thing or two about diesel fuel you know that they are pretty much removing the lubricity (that’s what is in diesel fuel to make it lubricate the injectors) so now you need the oil change to rejuvenate the oil that operates the injectors, especially fords, that oil gets compressed to thousands of pounds so it breaks down from being compressed rather than fuel contamination.