Mabilis ako mabawasan ng engine oil. Almost every 2 weeks naglalagay ako ng 1.5 liters of oil. Wala namang leak or oil droppings sa garahe ko kaya for sure walang tagas sa engine. Yung exhaust tip ko mabilis ding umitim kahit kakalinis ko pa lang after 30 mins driving eh may black deposits sa exhaust tip. I'm using 10W-30 and i also tried 10W-40 na para medyo mataas ang viscosity pero ganun pa din. Normal lang ba ito for old cars?
What should i do to avoid this or at least ma-minimize man lang?

Thanks in advance for your advice.