I took last Saturday to attend to my Prius. Once I hit 100k mi I knew I needed to get some things done. I changed out the oil, transmission fluid, engine coolant, and inverter coolant. I wanted to get everything I could while I had the under guard off. I have 105k mi on it with original fluids except oil and brake fluid. Transmission fluid was dark but no real foul smell. Nothing in the fluid but fluid. Both coolants were pink but just not as bright as new coolant. Nothing in the old coolant fluid. I have noticed the car running smoother and having more power when passing on highway. It's more peppy. The heater warms the car quicker in the morning and the engine goes through the warm up cycle faster and shuts off sooner. Just a few things I noticed in the last few hundred miles. Thanks @NutzAboutBolts for the maintenance videos! Cheers