Hey guys, sorry about the late reply. Had to wait 3 weeks to get a mechanic appointment. I didn't want to give you guys wrong info without getting it checked by the professionals. I did the final checkup this morning. It's been a ride and a half.
So, I got my car checked with 2 different mechanics. First one thought by the initial check up , it could be a bad turbo. Took it back to the same guy for detailed diagnose. He found nothing. He kept the car for 2 days just to see how it behaves in the cold start. No blue nor black smoke upon raving the morning. He found no oil leak either. That result wasn't the sort I was hoping. I thought, he might have missed something, so I booked one of the best mechanics around and had to wait quiet sometime for the appointment.
Now these guys found nothing at all. Even they're quite surprised that this model still runs smooth without any major faults. They did thorough checkup, turbo came out good, engine oil level came out almost at the same when I topped up about a month ago. I drove almost 1000 miles since then. May I also add, that I only topped up when it was totally dry and it was just 2 liter of 5w-30.
One thing they recommended that to use 5w-40 oil instead 5w-30 as its thicker. It might last longer but again its not guaranteed. Apparently that's how this one runs. And they also think the previous guy who I did the servicing with, they might have used wrong oil or something which wasn't meant for this car.
So I guess that's basically a dead end to this investigation. I got in touch with the nearest Audi dealership as well in between those two mechanics, and did a background check with them. There's no record of my one been recalled for any manufacturer fault.