i searched a little and didn't find any threads on maintenance on the mechanical part of your engine, so i thought i would add some advice.

1 - change your oil - it's the single most important part about keeping your engine healthy and running a peak efficiency. i don't care what you think about conspiracies about oil companies and the lies they created about changing your oil at a certain time so they can make more money. if that were true then when you changed your oil you would see golden brown oil come out of the oil drain pan. when your manual says 5,000 miles, 95% of the time it recommends synthetic oil. If you drain your oil and it looks blacker than the ace of spades, you went way over the life of your oil. you want your oil to be a mix of brown and dark brown. as oil breaks down it reduces its ability to lubricate. I've seen 15% fuel mileage increase when all i did was change my mother-in-laws engine oil in a n 05 impala and she was 2,000 past a 3,000 mile oil change sticker. some engines(mostly chrysler) they need changed at 2,000 miles because the engine cooks the oil so much. even if you changed your oil twice as much as you need to it would only cost you about 120 dollars a year more(or 10$ a month more). If you have gone over you oil change most of you life there is a light at the end of the tunnel. Sea-Foam, when i used sea-foam for the first time i could tell by the time i backed my car out of the bay and started to pull forward, that fast. here's what you do, change your oil and put 1 oz of sea-foam per quart of oil put in the engine. drive it for 100 miles and then change your oil again(a pain i know). bam, instant efficiency improvement. cleans out all the crap that the detergent in your oil can't keep up with because fuel quality has declined so much.

2 - check your air filter - another commonly overlooked part of an engine. when the air filter gets too dirty it can't give the engine what it needs more than anything. i've seen at an extreme 10% increase in fuel consumption from a severely dirty air filter. can't say anything about slightly dirty air filters

3 - spark plugs - not as common now that platinum has taken over. but if you have an older plug and it had "regular" spark plugs they are due at 30k mileage for a reason.

4 - drivablility - just because your check engine light isn't on doesn't mean you don't have a problem. lower to mid 90 ford's are the worst but there are many more out there. if the engine is not "smooth" throughout all parts of your drive something is wrong and is costing you more fuel. older ford's would "cheat" the epa and check engine light by shutting off fuel injectors if the misfire was too bad for emissions. if your car stumbles or hesitates when you push the pedal down your are losing fuel economy. just because it passes the computers test doesn't mean it is working as it should. mass air flow sensors are the most susceptible to this problem. if your tech says we can clean it and see how it goes, it will be better but it would work like a new maf and you won't get the fuel economy you would if you replaced it(unless it is very expensive). the problem is they get insulated by dirt and they don't respond fast enough to give you the proper fuel/air ratio at the proper load increments.

5 - wheel alignment - i know i said engine mechanical but if your alignment is off it causes more power from the engine to overcome the drag from the mis-aligned tires.
toe is the really the only angle that causes lower fuel mileage increase. camber causes a slight pull and tire wear and caster only causes a pull no tire wear or fuel mileage increase. in most cases its good to get an alignment once a year.

6 - tire pressure - tire pressure checks are now a law in california. tire pressure is very important to fuel economy. i always put my tire pressure within a few psi of max tire pressure on the tire. the manufacturer recommends a tire pressure on the sticker in the door jam but that is a compromise of comfort and fuel economy.

7 - intake service and/or fuel injector service - removes carbon build up from intake. works good. i could tell the biggest difference under light load. my car was much more stable.

8 - underlying problems - like the previously mentioned problems any sensor that doesn't read correctly won't give you the best fuel economy. unfortunately it usually doesn't show up until its bad enough to cause a misfire. one over looked problem is alternator diode ripple. under load the alternator diode(the part that converts ac to dc leaks) likes to leak ac current which throws the computer all kinds of left hooks. can cause minute problems all the way up to check engine lights to misfires.

if you want the best out of your engine make sure it is up to the task mechanically electronically and alignmentally.

forgot to mention using a thinner grade of oil is better in colder weather and will give you better fuel mileage because there is less drag on the internal parts of the engine.
i recently switched from my manufacturer recommended grade of 5w-30 to 5w-20 and i noticed a huge improvement in cold start up noise. which is where a lot of engine wear occurres because the oil is too thick to get where it needs to be fast enough. most car manuals give you a range of temperatures and the recommended oil weight for those temperatures. but i know most people are scared to change oil weights so its up to you (google it if you're not sure)