I may not be as old as your Grandfather.
However, in the 1960s and forward, no one I knew was changing oil every 1,000 miles.
In the 60's and 70's my high performance 400 + HP daily drivers were getting changes once every 2,500 to 3,000 miles. This change was primarily necessary from the high ash content in the east coast sourced oils. It caused a waxing and frothing that could block the smaller oil passages causing damage to the engines.
Currently, I change my 48 year old supercharged engine at about 1,200 miles or two years. Primarily this is from water absorption into the oil, that does not get burned off unless you run long enough and hot enough. Additives may break down with time.
I didn't know of folks ignoring changing their trans fluids back in the 60'2 and 70's.
egads' advice to stay timely with maintenance plan or more frequent on trans fluid is a solid recommendation.
Check with Honda before changing your oil the first time. Any color change you see in that first 1,000 miles may be from the protective lubricant molybdenum used in engine assembly being dissolved into the oil. Personally, I won't be using cheaper oils that might not have the correct additives specified by Honda.
On my 48 year old supercharged engine, when changing the oil, I need to add specific additives, since they have been reduced in today's oils.