Dear, use Zic 20w50 oil if your car is drinking such amount off oil.
I dont know the good mechanic, but i have went through this overhauling process.
What is did?
1. I went to different mechanics for this job and got the estimate of labour and parts
2. Then i got information about the good spare parts dealer.
3. After a week, i selected one mechanic, purchased all spare parts by myself, and got done all "Kharad" job before my eyes.
For four years, car didnt created any problem, recently got gasket replaced.
Now the car is in use of my elder brother