gas mileage 2013 azera

I have a 2013 Azera on recent trip got 30 mpg for 3 tank fulls. After that it keep going down to as low as 24.5mpg. Also noticed that I could feel the trans shift down on hill climbs have not felt that before. Do I need the trans fluid changed it has 66000 miles on it. Are there other issues that could cause this

 

Doubtful ATF is the cause.

It's easy enough to check automatic transaxle fluid (ATF) level. And it's a prudent to do so regardless of any perceived issues. The fact is however, ATF level has to be really low before it affects transmission operation.

Degrading fuel mileage is yet another endearing characteristic of the Azera, the engineering embarrassment of the Hyundai offerings. Admittedly, it is rather peculiar that your mileage went down on a trip; usually, mileage improves during a long, contiguous slog in that car (...most any car, really). Investigating the sudden onset of decreasing MPG does not involve ATF levels. The first thing you should check is the tires; the check list proceeds from there (and gets more complicated).

Intermittent less-than-smooth transition between gears on a hill isn't particularly unusual. If transmission slams (hard shift) or "flares" (high RPM on tach) between gears you've got something worth investigating. If either of these are your experience—hill or none—check the level and quality (color) of your ATF.

As for changing AFT...
First check your Azera's maintenance guide for the specific recommended mileage and time intervals for ATF changes. Or, you can go with the laymen's method of AFT changes: Drain and refill three quarts of ATF at every oil change. At 66k, you are overdue for a change if one hasn't yet been performed on that car.

I don't recall if the 2013 has a transmission filter—your Azera's maintenance guide will know. If it does, follow the recommended replacement mileage and time interval for that thing as well. If that vintage Azera lacks an external ATF filter, consider installing an aftermarket external ATF filter. They're important.

Finally, consider purchasing a DTC reader. This inexpensive widget plugs into a port just inside the driver's foot well and reads any trouble codes stored in the Azera's computers: both the engine management computer and the transmission computer. (Look for a model that reads ABS and SRS codes as well.)