When am i going to change 12v Battery and transmission oil type

1) anytime it causes you trouble. All car batteries are good for 4 years unless abused, some will last twice that.

2) ATF WS I would.

 

I have no idea if other CVTs use ATF WS, I don't own them. The Prius uses ATF WS.

 

1. If the battery's giving you no problems I wouldn't be too concerned yet. You can get rudimentary check by measuring it's voltage when the car's at rest. 12.5 volts or higher, it's in good shape. 12.2~12.4 indicates borderline, dying. Lower: immediate intervention needed, charging and/or replacement. Still better though, is to get it's voltage AND Cranking Amps tested: there are electronic testers to do this now. Battery retailers should have them.

The brake "prolonged whirring sound", if this is just when you've opened driver's door: it's normal, the system pressurizing.

2. Don't mess around with alternate fluids. Toyota is very clear: use Toyota Genuine ATF WS. You don't want to experiment with this, the transaxle is expensive. Toyota says nothing about changing the fluid, but it's good to change it, and sooner than later. The first change is more critical. Once that's done you could probably leave it for life.

 

The battery looks "ok", but maybe start looking, have some sources ready.

 

Best if you could get the ATF from a Toyota Lanka outlet, that way you can be sure its genuine.

About the fuel efficiancy you can check the following:

- Check tire pressure (33 front 30 or more in the rear)
- Does the air filter need replacement
- Are you using SAE 0W-20 engine oil or did you switch to something else

12V battery in the Aqua is different from the typical battery you get in a petrol car, always replace it with a maintenance free battery as it is inside the car. I don't think AGM batteries similar to the original battery are available locally.