brother Tabish,
What are the updates about your Car now? Has your problem solved?
If you are using havoline 20/50 and having it change from "same shop" for years, then next time try to have to change from another good shop. No offense, but this problem may be because of poor quality of engine oil you are using!!
We own an oil shop brother. And different distributors always gave similar options to buy local oils of same viscosity but at different prices.
For example, recently a distributor of a local company visit us. They offered us
20w-50 oil of "same company" at
~ Rs. 1100/4L Grade 3
~ Rs. 1250/4L Grade 2
~ Rs. 1600/4L Grade 1 genuine oil.
We just simply said "sorry" to him and he went away. But he taunted that less than 20% people her in Pak. using Grade 1 oil. Majority using Grade 2 & 3 and making big profits. But pity is that how many consumers (we all) know this fact about these fake oils available of same company in same city/country?
Hope this example is good enough to clear our visions about local oils.
Cheers.