If you want your transmission to last as long as your engine - i.e., past 120,000 miles for 4 cyl., 160,000 for 6 cyl. and 240,000 for 8 cyl. then the following rules of thumb are a good guide:
1. For non-filtered transmissions - typically Hondas - whether regular or synthetic (typically regular) - do a complete fluid change every 15,000 miles or as needed.
Hondas are pretty easy - most can be done at home. It’s just like an oil pan - drain - and refill.
2. For filtered transmissions - sealed or non-sealed - whether regular or synthetic (typically synthetic or blend) - do a partial fluid change every 30,000 miles or as needed.
DO NOT DO COMPLETE FLUID CHANGES ON FILTERED TRANSMISSIONS THAT SEE NORMAL USE. THAT CAN HARM THE TRANSMISSION. PULL OUT THE MANUAL FOR SUCH CARS AND IT’LL TELL YOU EXACTLY THAT.
One of the early mistakes made at “Jiffy Lube” like centers early on was the “complete fluid flush” service that was offered on ALL TRANSMISSIONS. A lot of these centers got hit with suits early on for damage to transmissions that required partial fluid changes. They’ve wised up nowadays...
=8-)
I just hit 80K miles on my 05’ Honda Pilot and had the dealer change the transmission fluid for the first time. They wanted me to change it every 30K miles. At 80K it was as clean, non-burnt, as the day it went in.
15K or 30K transmission fluid changes are a complete waste of money.
I’ll probably wait until 150K to change it again.