I own a 2005 Prius that I've
I own a 2005 Prius that I've had for ten years. I do all of my own maintenance. All of the Toyota hybrids use a planetary gear set to combine and also separate the power from the two electric motors in the transaxle and the internal combustion engine. The gear set is at the heart of what creates the "synergy" between the engine and the two electric motors. All Toyota hybrid transaxles do require the use of the Toyota WS (world standard) transaxle fluid to lubricate the planetary gear set and the final drive gears. The capacity for my second generation Prius is four quarts. And I change the fluid every 60K miles.