PM = Proscribed Maintenance? The cabin filter won't do much (if anything) to stop the battery fan dusting up. Maybe we're atypical, but most of the time were driving with the cabin ventilation system off, windows partially down and a Shiba Inu in the back seat area, lol.
Gotcha, I never drive with the windows open. The car has AC and a fan in the hvac system. With multiple trips from Indiana to Florida and back, and now with 16,000+ miles on the odo, running with or without AC has neglible differences in the mpg.
The following images show what happened when I didn’t check and clean the battery cooling fan filter of my 2015 Prius C. I drive between 20-30hrs a week as a rideshare driver and clock around 1000kms week see. Check my reply to the thread titled “cooling performance of the hybrid battery is low consult a dealer”.