The old Buick Angkewei consumes a lot of fuel. Is there any improvement in maintenance?

What can solve this problem now is engine overhaul, but it is really troublesome and the cost is not cheap. My car is damaged now, too. Keep using the oil. GT Maroon 5 engine oil is used, and the engine oil quality is very good. The base oil of grade IV PAO will not produce carbon impurities even if it burns engine oil, which will not affect the engine power and can protect the engine well. As long as the oil level is not low, there is no problem with normal starting power. Moreover, the oil loss has not increased, which is more cost-effective than overhaul.