The economy in oil changing is not related to the cost of the oil versus the mileage until the next oil change. The economy comes from extended engine life.
Even Mobil One is much cheaper than engines or cars.
The only way to clean the inside of the engine is to drain the oil. The same amount of contaminants are produced by a given engine regardless of the oil used.
Change oil hot and change oil often,
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in