New (pre-owned) 2016. Things to do?

Congrats on your new purchase!

If you are gonna keep for a while, yes many (including myself) will recommend to change trans fluid.
Also, do a brake inspection and lube those caliper slide pins!

 

Engine air filter and cabin air filter are often overlooked. Check coolant levels in the engine and inverter systems. Should be clean and bright pink in color. 12V battery is under the hood beginning in 2016. Also, it is a classic wet cell style, not AGM, so you can unscrew the caps with a quarter and check the electrolyte level.

 

Toyota’s recommendations are in the Warranty and Maintenance Guide (PDF). I’d also suggest checking each of the items listed in the Owner’s Manual (PDF), under “General maintenance,” pages 581–583. Here are some further suggestions:

• If you don’t know when the engine oil and oil filter were last changed, or whether the proper grade of oil (0W-20) was used, consider replacing these at once. As @FuelMiser kindly mentioned, checking the engine and cabin (air conditioning) air filters is a good idea, too.

• A filter that’s often missed is in the air intake for the hybrid battery. Toyota didn’t show it in the Owner’s Manual for 2016, but the Owner’s Manual (PDF) for 2017, pages 573-574, shows the location and basic cleaning. If you find dirt, pet hair, etc., you may need to clean the filter more thoroughly or replace it; see the Repair Manual (more info) under Engine/Hybrid System: Hybrid/Battery Control: Battery Cooling Filter.

• If the original windshield and rear window wipers are still installed, replace the rubber inserts (2016 Owner’s Manual, pp. 624–627). Toyota dealers sell the inserts, part numbers 85214-47110, 85214-78010, and 85214-47010, for about $10 each.

• Make sure you have at least two keys (wireless key fobs) that can each unlock and start the car, and that have mechanical keys that work in the driver’s door lock. If not, consider having a second key made, to keep in a safe place. If all the keys are lost, it’s more complicated and costly to replace them.

It’s PriusChat folk wisdom that it is, but I don’t know that anyone has strong evidence that purging its black humours actually increases the useful life of the transaxle. It’s unusual to hear about mechanical problems with transaxles on Prius cars, anyway, since the gears are always in mesh, and there is neither shifting, as such, nor hydraulic control as on a conventional automatic transmission. (The fluid is for lubrication and cooling only.)

In the maintenance schedule, Toyota mentions replacing the automatic transmission fluid only as an additional item for “Special Operating Conditions,” that is, “Driving while towing, using a car-top carrier, or heavy vehicle loading.” If this applies, the fluid is replaced at 60,000 miles or 72 months, and again at 120,000 miles or 144 months. If you don’t know how the car was used before you bought it, it might make sense to do this once, anyway. If you do, use Toyota ATF WS; unlike Type T-IV, DEXRON, or MERCON fluids, this is a proprietary specification, for which there are no licensed or approved equivalents.

 

what country are you in - your profile is blank.

 

There's at least a couple of locations for pdf versions of the manuals (Owner's Manual and Warranty and Maintenance Booklet, in the States*). Toyota Tech Info is one, in the "Manuals" tab. Very handy; I use the pdf versions more than paper ones, by far.

* There's some others too, manual for the Navigation for example, IIRC.