Vehicle: Gen 6 Honda Accord V6 Lx
B7XA Transmission: The current transmission in this vehicle is a replacement that was installed 10+ years ago. However, the vehicle has been a back up vehicle for those 10+ years and has only accumulated close to 30,000 miles since the replacement transmission was installed.

My Accord is at the 30,000 mile ATF fluid change interval and as I’ve been researching into changing the fluid. I’ve come across 2 different processes.

ATF Fluid change: This process empties out the existing ATF and adds back the required factory spec. From my research, this process seems to leave behind an amount of the old used fluid in the system.

ATF Fluid Flush: This process pumps new ATF fluid through the entire system flushing all the old fluid out of the system. Once the fluid coming out of the system looks clean, the pumping is stopped and the correct amount of fluid is left in the system.

Which process should I use? To me, it doesn’t make sense to leave any old fluid in the system if I’m trying to take care of the transmission. Should I just do a fluid flush or a fluid change?

 

Honda ATs are low pressure units, more related to an MT than a typical planetary gearset AT.

Proper way to change fluid is to drain, refill, drive through all gears and repeat two more times after. 3X total.
You'll never get all the old fluid out, diluting the old with new is the easiest and best way.