Originally Posted By: TomYoung
Once a car starts consuming oil, you can quickly move to just changing the filter, because when you are topping up the oil, you are changing the oil.
I think Im taking the bait but...
Disclaimer: Im not going to agree or disagree with the above statement but just thought I would mention a couple of items.
Some owners manuals (CAT Engines for instance) actually vary the oil change interval based on the addition of oil.
Some engine manufacturers actually have a system (Cummins for instance) in which oil is pulled from the crankcase and ran through the fuel pump to be mixed and burned with the fuel while this oil is replaced from a reservoir that is kept full. Filters are cleaned (bypass) and replaced (full flow) at regular intervals and the crankcase is only drained at several hundred-thousand mile intervals which I believe coincides with running the overhead (Adjusting valves, injectors, engine brake, etc).