Unexpected drop in fuel average after oil change

[pwuser154853009897]

Dear friends
My Honda city 2012, MT was giving me around 16 (15.9) KM/L, for past 6/7 months. I got the oil change last week and got it refueled from the same station where I normally do. The oil was changed by Honda avenue, Islamabad. The guy out sm-5W-30 as usual. Oil filter was also changed. Air filter was in good condition as it was changed last time (6000 km ago).
After this stuff was done, the average has dropped to 13.5. Nothing has changed otherwise. My route is same. I drive it myself. It has been driven in Islamabad only. I mean each and every thing is same except for oil change.
What could be the possible culprit? How to bring back her fuel average?
PS. 1. Fuel filter has not been changed at 80K. Now it has done 89K.
2. I get it refueled at same petrol station and get only normal petrol.
3. Drive on express way only.
4. Has been refueled three times since this oil change. It has done almost 1000Km since this oil with average hovering around 13.5-14.
Suggestions from experts are needed.
Regards

[Mirza967]

Reset the meter

[jklodhi]

Check catalytic converter

[crude101]

dont do anything just reset the meter. the grade 5w30 is the right grade oil. Just drive for some days and check after re-setting.

[pwuser154853009897]

Dear all. The values posted (16 and 13.5) are reserve to reserve and have been calculated not the value shown at odo. Moreover, the car has been driven almost 900km after oil change, with value hanging about 13.5-14. So, setting the meter wouldn't do any thing, I think.
Any other culprit?

[hash4u]

check tire pressure
how is the pick up?any change?
which petrol station do you use? try switching to more reknowned one

[pwuser154853009897]

I'm using normal petrol from Total station opposite to Quaid monument at expressway. I keep tyre pressure as per company directives. The pick and every other stuff is same as before. I did not notice any thing suspicious other than the drop in average.
I'm going to change air filter today, as a first remedial action. I suspect it to be the culprit. The car has driven 7000 KM on this air filter.
If this does not work, which other thing should be considered then?

[hash4u]

Nice catch
A blocked filter will surely effect
If the pick& performance is fine I won't suggest fiddling with anything else
Also try tank full from attock H8
Shell F6 or total F6 . Maybe that total u use recalibrated there measurement etc

[hasan.zaheer.me]

When he did not even touch the air filter, how are you guys suspecting that air filter will be the problem.

Anyway, please do keep us updated. Let us know what happens.

[pwuser154789791395]

Is this issue diagnosed. Because yesterday i changed oil 5w30 from honda fort motors. I traveled on motorway from isb to lhr with ac gets 16 km average at 120. But after oil change get 14 km per L without ac.my car model is honda city 1.2 mt 2021.