If you've never had your coolant replaced, change it. There are lots of videos on how to change it, either Scotty or otherwise. If you have crud building up in your radiator, it can't do its job as efficiently, you need to change your coolant. You want to keep it as clean as possible, your radiator and heater core will thank you. Don't flush your transmission, only do a fluid change, and keep your old fluid in case it starts to slip. Toyotas aren't like Ford or GM where if you do twice the mileage on the original fluid, then attempt to change it, it more than likely will start to slip, but have it on hand, just in case.

Posted by: @tnewki3

I am afraid it will loosen up other things in the radiator or heater core.

things like what? I've never heard of this issue.

Just flush it out.

Posted by: @tnewki3

I had the trans fluid replaced on my Ford Fusion at 50K miles and it has never shifted right since

a failed trans at only 50k? well it is a Ford I guess.

See our FAQ about trans.

Those hybrids have two cooling systems, the normal one, and the inverter. The inverter is very expensive, you should go ahead and change that too.

The CVT is very easy to do, similar to a normal differential. All it is, is a drain bolt, and fill bolt. As @justin-shepherd mentioned, this is one of those times that you can drain the fluid, and keep it on hand in case something actually goes wrong with the new fluid, not likely though.

https://www.youtube.com/watch?v=88Y7mVa-a7o