Shall I change the this liquid as it low now

That's very likely the brake fluid reservoir, and the fluid would be DOT3 brake fluid. Toyota dealerships offer their brand of fluid, which would be safest, but any fluid of description "DOT3 brake fluid" should be fine.

If the level is low there are two possible reasons:

1. Your brake pads are nearly worn out, in particular the front, disc brakes. Normally brake fluid level in that reservoir drops as pads get thinner. Topping up the fluid in this case is not a good idea; you'll likely fine if the pads are replace with new, as the brake caliper piston is pushed in to accommodate the new pads the level of fluid will rise up to the top mark again.

2. You have a brake fluid leak. This should be checked out right away.

Also, periodic brake fluid change is a good idea. Toyota in Canada recommends tri-yearly or 48,000 km's, whichever comes first.

 

I love the thoroughness of misinformation on a forumWhy don't you add some distilled water and monitor over time. It's the inverter coolant.

 

Whatever.

Yeah, you got me.

 

- It's the inverter coolant reservoir.

- You should top it off to the "Full" line using Toyota super long life coolant (pink - comes as a 50/50 premix).

- If you have lost fluid then definitely try to find out where it has gone. You probably have a leak.

- If you have lost a lot of fluid (like if it's not longer even visible in the reservoir) then you'll have to be very careful that you don't have air locks in the system.

 

Changing the inverter/transaxle coolant is a little involved and it's critical to get it right. Get detailed instructions and be sure you understand them completely before attempting it. No special tools or skills are needed, just a short length of tubing, a couple of wrenches, a bucket and a funnel. It takes less than a gallon of Toyota antifreeze at $25. It should be done at 100,000 miles maximum.

It's likely the engine antifreeze should be changed at the same time, but that's much more involved and you need the Toyota scan tool. If you hire a mechanic to do one of them, get them to do the other, too, and make sure they are familiar with the Prius and have the proper Toyota tool.