To check which transmission fluid goes into your car, check your owner’s manual. It will give you the exact fluid & specification why go you need. Don’t use the wrong one, or it’ll ruin your transmission.

For the best gas mileage, there’s a few things you can do, but start with cleaning or replacing your air filter, inflate your tyres to the correct cold tyre pressure, check your spark plugs & replace if necessary, however, the most important of all, change your driving style. 

You’ll be surprised by how much gas mileage improves, with just a change in driving style!

600km on each full tank is still decent for the Camry, in the city though. 

the factory fluid is Toyota brand Automatic Transmission fluid WS.  I haven't been able to find it in stores, but it is on amazon,  I'm sure the dealer could sell it to you, for about 500% markup haha

I always recommend going with whatever oils and fluids the manufacturer recommends. That way you know there won't be any issues.

As for maintenance, my wife drives a '15 Camry and we get 34MPG pretty regularly at 75k miles on the clock. Just following the manufacturer recommended maintenance is good enough.

Alright guys, that was extremely helpful. Also if I were to do services such as Injector cleaning, Catalytic converter cleaning, etc. as a complete maintenance on 200k KMs, would it be helpful or is it needed? My car runs okay no issues, just want to make it smoother. What's your opinion about this guys? Or if any of you can suggest me useful and required/recommendations for a 200k service on my '15 Camry?