If you drive normally and use conventional oil then my recommendation is to change the oil/filter every 5,000 miles. If you use synthetic then change it every 8,000 miles. If you drive in very dusty conditions then change it more often. If you drive mostly highway miles then move to 6,000 miles conventional and 10,000 miles synthetic. Or you can follow the manufactures recommendation listed in your owner's manual which is always best.
When it is time to change your oil, you should change all of the oil.
Change oil/filter every 5,000 miles.
once every season
If it is the 3.0l, change the oil every 3 months OR 3000 miles and that engine should last you forever If it is the 3.0l, change the oil every 3 months OR 3000 miles and that engine should last you forever
You should change engine oil in car or truck every 5,000 miles.
If you intend to keep your vehicle's engine clean, change it every time you change your oil. The filter holds the dirt your engine generates. Hence the dark color of your oil as it ages and is pumped through your engine. Dirt is dirt. Get it out.
once every season
once every season
You should since it increases longevity just like changing engine oil does for the engine.
Every other oil change.
If the 4.6 liter is in a Ford Expedition it should be ( 6 quarts ) with engine oil filter change
1976 Chevy 350 engine should take 5 qts engine oil with filter change.