Limited experience w/diagnosis of those sensor signals, but to me it appears the o2 sensor before the cat (sensor 1) is not working correctly. It isn’t going up and down every few seconds like I’d expect to see. For example like the signal in the first diagram in Tester’s post above, under “normal operation”. This presumes it is a standard binary zirconium lambda o2 sensor. If it is a wideband sensor then the signal may be ok.
The other signals look normal, except for the long term fuel trim, which is biased to about 5.5% negative as I recall. That’s within normal range, but if any of those signals is a clue to your mpg problem, that’s the one I’d focus on. (That could be caused by the unexpected o2 sensor signal I noted above.)
There’s a second long term fuel trim labeled “total” which is biased at nearly 0%, which is good, but I don’t understand how the long term could be negative 5.5% and the “total fuel trim” 0%. Does your manual have an explanation for the difference in long term and total fuel trim displays?
As far as your decreased mpg, the most common reason sans testing evidence is usually the engine is running under the designed operating temperature, due to a faulty (partially stuck open) thermostat. Something like that wouldn’t be unusual at all in an 8 year old vehicle. Thermostats tend to warp a little as they age and don’t seal 100%.