The dealer changed the fluid two years ago so I didn’t contact the dealer about this since the fluid was changed a while back. Late 2025 and going into the start of this year was when I started noticing the fuel economy decrease and some subtle shifting abnormalities, like not shifting as smoothly as the vehicle did before the fluid change. Another thing I noticed is at 50 mph when the torque converter locks up, when I let off the throttle and then reapply throttle, the rpms rise slightly then goes back down slightly, much like the torque converter locking up again. I don’t recall the vehicle doing that before the fluid change which caused me to get concerned and suspect something was up with the transmission. The car has a 4-speed transmission and the torque converter locks up in 4th gear at about 50mph.
I had a local shop (not a dealer) look into this and they ran their scan tools to check for codes and view other metrics for the car and didn’t see anything abnormal. They test drove the car and did not observe or feel anything abnormal. I will say that I drove this car for years and would notice something that’s slightly off. However, to someone else driving the vehicle, they may not feel anything’s wrong and would say the car is shifting normally. The mechanic I talked to said if there’s something is going wrong with the transmission, it may take some time for noticeable symptoms to present themselves like an obvious rough shift or transmission slip or codes to appear. They looked at the spark plugs and the air filter and they looked fine.