when do I need coolant and inverter fluid changes for 2013 Toyota prius??

welcome!
either 100k or 120k. if you did not get a maintenance schedule book, you can find one at the toyota owners website
the only things between 0 and 100 are oil, filters, tire rotations, brake caliper slide pin lube and inspections

 

tranny fluid, brake fluid, and all the cleaning of the egr and other stuff lol

 

You mean the two coolant circuits, engine and inverter?

In the States:

engine coolant: 100K miles or 10 years (whichever comes first)
inverter coolant: 150K miles or 15 years

And thereafter:

engine and inverter coolant: 50K miles or 5 years

 

What happens if you never change the coolant? Our 2011 Prius has 232k miles but afaik we've never changed any of the coolant except the engine coolant just now as part of head job, but I don't plan to mess with the inverter. Its coolant still looks perfectly fine, as did the engine coolant and the parts in contact with the coolant that I disassembed.

 

Probably a video named “Prius fireball” that will emerge, go viral and be shared on here maybe 4 or 5 times.

 

Old coolant loses it's anti-corrosion ability? FWIW, Toyota Canada says to change both circuits at 100K miles or 10 years. That's a long interval btw, compared to other cars.

Google for more info.

 

might lose anti freeze protection

 

no. and you could save a lot of money doing those filters yourself.

the cabin filter gets checked/cleaned/replaced every 15k, and the engine air filter every 30k

 

Maybe...

 

Coolant helps dissipate heat from the engine, over time, the coolant loses the chemical to cool down the engine so your engine will overheat. They do sell coolant strips to check if the coolant chemical is still in standard or not. I usually change my coolant every 120k miles.

 

When you DIY the air filters, you might a get a new perspective on their condition. Maybe being further north and on the west coast is a factor, but over 9 years and 84K kms, I've yet to change either. The engine air filter in particular looks almost new still.

It's not chiselled in granite, that you must replace them, if they look near-pristine.

 

Not unless you've been diluting the coolant with water. You might lose corrosion protection, because the pH will eventually go acidic.

I just had my engine coolant "flushed" (whatever that means!) by the dealer for about $117, including one(?) "unit" of new SLLC, $20 off in coupons, and a(n invisible) "flush kit." A few days later I got a coupon for "Winterizing Service," including draining coolant and up to one gallon of SLLC for $99. Unclear what's the difference.