Poor fuel economy
 

Hi everyone new guy here. Last November I picked up a 1996 Accord sedan, 2.2 auto. Had about 185,000 miles on it when i bought, currently has 195,500. Ive been using it to deliver pizzas. My fuel economy has been what i would consider OK but no that great. I'm averaging right around 20 MPG in city(stop-start, short trips) and only about 27 on the highway. I've replaced a number of parts in an effort to better that number but nothing has help. heres the list:
Plugs
Wires
Distributor(full assembly, including cap/rotor)
Coil
Upstream o2
PCV valve
Changed to full synthetic oil
Changed trans fluid(genuine Honda fluid used)
Thermostat
It does have a set of 17" rims with 215/45-17 tires, weight wise they are almost the same as stock, and i was getting the same poor economy before the wheels. There isn't any extra weight in the car(no stereo or anything). Just had the alignment done.

Now i know that 20MPG doesnt seem that bad but, considering in my old s10(4 cylinder/5 speed) i was getting 24, or in my old Subaru(4 cylinder/5 speed) i was getting 30, 20 is barely ok. I believe that the biggest thing hurting it is the auto, it is very stupid, and like to hold gears for longer than i think that i should. So is there anything else that i can do? Sorry for the long winded post, any input/advice would be greatly appreciated, thanks

Tires are not stock and do create more friction based on the tire size. MPG all depends on driving style, how much it idles etc. as you are well aware of.

Actually, if OD of tire is larger than stock the fuel economy is under stated since mileage will be lower (larger diameter tire covers more miles per revolution and mileage indicator measures drive shaft rotation and miles based on OEM tire spec size.

I attach a simple spreadsheet you can use to calculate how much your mileage will be undercalculated. Diameter ratio is about 1.06 and mileage loss will be inverse 1/1.06 or 0.94. So you lose about 6% of miles which will mean your mpg is 6% low or about 1.3 mpg lower than actual. You will need MS Excel to use spreadsheet.

An older engine may have lost compression which will reduce gas mileage.

An OEM thermostat will allow fastest warmups (less time in open loop engine control), and higher operating temps which improve efficiency. If you installed a cooler thermostat 180 or lower, this can reduce gas mileage.

good luck