2002 Prius. What type of coolant do I use for my engine, and what type for the inverter?

The gasket for the transaxle pan can be ordered at your local toyota parts desk. Get the replacement washers too for the drain plugs. Lets see I believe they use the same "red" toyota longlife 50k mi coolant in both the ice and the inv. You probably could use regular 50/50 antifreeze in the ice, but I don't think I would use it in the inv. I just stick with the toyota long life coolant for both. It costs a bit more, but it does stay longer too.
The transaxle oil in your 02 should be replaced with toyota type T-IV only.
Hope that helps off the top of me head..

 

If you want 50K mile service life coolant then you would buy Toyota Super Long Life Coolant which has a pink color and is already mixed with distilled water.

Some older Classic were equipped with Toyota Long Life Coolant which has a red color and a 30K mile service life.

Both are priced approximately the same, ~$21 per US gallon. However SLLC is premixed while LLC is not mixed. Since distilled water costs ~$1 per gallon, the effective price of SLLC is around 2x LLC.

I would avoid using some cheap antifreeze that you can buy at your local discount auto parts store.

 

$42 for 50,000 miles of coolant service life is cheap, it seems to me. $10 for 2 gallons of 'whatever', followed by possible damage to the inverter due to compatability issues there sounds expensive by comparison.

If one cannot bear the cost of Toyota's LLC or SLLC, there is a compromise of sorts. Equip the inverter loop with the correct coolant, and use 'whatever' in the engine coolant loop. The latter is pretty conventional and chances are you won't hurt it this way.

 

If both red and pink work, just buy red for the inverter, and when you have to dilute it with water, you'll have enough for your engine free vs the pink. Looks like the dealer only gives you 20k more service life for the SLLC while charging your twice as much as the LLC. I guess it saves you the labor of draining and refilling. Sure gotta wonder though, since red+water=pink.