gas mileage

Ive got a 98 auto 2.0 sedan that is getting 21 mpg. Ive changed fuel & air filters, both O2 sensors, mass air sensor, wires , platnium plugs & about 5 tanks with Lucas fuel treatment. I started about a year ago trying the easy things & progressing up to new O2's, plugs & wires The only used parts were the mass air & both temp sensors from a parts car i have.
It started out with a lower idle (750 range) & not really effecting driveablitly, cruises well, starts every time. Tryed spraying carb cleaner aroung all areas to find a vac leak.
I plugged in my Actron scanner & compaired the diagnosistiges to two other Escorts & the only things that caught my eye were long & short fuel trim read outs.
Its been a few months since I did this & dont remember the number differences.
Its 20 degrees outside so im going to wait till it warms up to try anything. I have a total of 5 Escorts & 3 of them are getting under 25mpg.
Anybody got any ideas?

Fred

Has it ever gotten better mileage than that? That is; have you had it since before the mileage dropped to 25? I would try a compression check, to eliminate leaky valves or a lifter problem. And depending on the mileage I would wonder if the cat. converter or exhaust system was semi-clogged.
We have a 92 Escort (1.9 auto) that gets us 30 or 31 mpg on the highway, and about 26 or 27 in local driving. And our local driving doesnt involve much time in heavy traffic. (Im retired and can avoid the rush hours). Thats the mileage it got before I rebuilt the engine and tranny - and its the same since the rebuild. Though now it uses less oil between changes and doesnt smoke on startup.

It has 91k on it & got 29 mpg before. when it warms up outside im going to dig deeper into trying other parts from my parts car & check compression. The idle change one day at a red light & never came back to norm which makes me think vac leak or sensor. I agree with a simi clog cat too. I forgot to mention that i had a K&N air filter on it for about 9 months, but read a guys forum that it lowered his mileage. so i put a stock one back on with no inprovements. I just didnt try anything for a while & am trying the easier thing first. Thanks!