Change it according to the manufactures recommendations as listed in your owners manual.
Whenever it gets dirty.
every 3000 miles
5000-7500 miles
if your car's belt has bits of fabric coming out
Every 15,000 miles.
Every other oil change, drain water valve once a month.
I would say at least once every 3-4 months.
Every 4000 miles. Change it when oil is changed, along with oil filters
I change my oil in a 7.3 power stroke every 3000 miles no motor problems 240,000 on motor
The manufacturer recommends that you change the oil in your Range Rover 220 Turbo diesel every 7500 miles. The oil should be changed at least once per year.
Exactly as listed in your owner's manual. If you do not have one, I suggest you get one and not take a chance.
Every other oil change