500ml in 5k km is not that much.
When does your car give out smoke ? and at what rpm ?
My car gives out visible clouds of blue smoke around 4800 rpm ... below that there may or may not be any oil burn, its not visible. Right now its consuming around a litre of oil every 3500km .. which is when i just get the oil changed.
I dont think the o2 sensor had anything to do with the smoke the car was emitting. I think the fuel trims go haywire when the sensor goes bad and you may consume excessive fuel
If you have smoke coming out at high rpm or under heavy load, then its probably the rings.
If its on its first start in the morning, might be leaky valves
I think on these engines the vvti system can get clogged as well and lead to oil burning but am not sure.
My story in short.
One fine day while cleaning the throttle body noticed that there were huge clouds of smoke coming out at high rpms
Showed it to 3 different "trusted & renowned" mechanics, two said engine is dead and needs to be swapped one said maybe only rings will be needed when he opens it up
Showed it to a few dealers, all of them checked for oil burn and said its normal for older beltas/vitz w original engines to be burning oil and they will fetch low prices.
I asked what will they fetch with a swapped engine. That was also a lower price.
So I thought I would just run the car to its grave, but should make the journey for it a bit easier.
So I went to get its catalytic converter cleaned. The guy destroyed the o2 sensor while cleaning it.
Bought chinese replacement from gariparts (Phone: (021) 35801575). You can google them, they are located in phase 2 ext dha.
I also replaced its CVT fluid. It was dark, burnt and definitely overfilled.
Anyway, the car now has run another 24k km over 30 months since I was told it needed an engine swap/rebuild.
Its a bit slow and consumes a bit of oil. But cant be bothered for daily office runs in traffic.
I just clean the throttle body and valves before every oil change because they get clogged from all the oily fumes.
Why did my engine not last long enough ? I can think of the following reasons
- using fake oil filters
- running the car for over 25k with an overfilled cvt transmission ( it used to whine a lot )
- getting the engine "flashed" twice at oil changes (flushed. I didnt know better. The oil change ppl drained the oil, poured some crap into the engine and let it run a few minutes before draining the fluid)
Regd scanning, I have my own obd2 scanner but you can get it scanned from any proper place. Charges vary, depending upon shop location and your dress/appearance 
Also, Shell doesnt sell 10w-30 .. Ithink they sell 5w-30 and 10w-40.
