Fuel Milage

So this morning I decided to go for a small drive... 600 mile round trip to my moms house in Florida to cut her lawn. The little voice in the back of my head (My girlfriend) told me I should take my Chevy (I have a 99 S10 2.2 Auto with 85k) and I have my B2000 (2.0 5 speed). The chevy around town sucks on gas about 16-18ish, but on the open road I can get about 28mpg. The B is even worse (the little voice was not about the gas usage it was what if you get stuck)

I drove the Mazda from Mobile to Panama City Beach and averaged 21.8Mpg driving approx 60-75. That just doesn't sound right. Any one know what the millage should be or how I can improve it. I got 280 miles out of 13.3 gals.
Here is what has been done already.
New Plugs & Wires
New Air filter,
2 new fuel filters
Fuel system cleaned (Previous owner had it done at Firestone about 2 months before I bought it)

What do I need to do??

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so your only getting about 280ish too? And here I thought I was getting crap mileage out of my 2600i....I get about 250 in townish driving...mixed some highway too and from and various light to light driving.......and I havent even started in on the fuel systems yet

I've got a 1993 B2200 EFI, and i get around 22.8mpg with normal driving (about 60% highway). However, the odd time i get as good as 27 mpg (when i drive 100% highway with a steady gas pedal) or as bad as 18 mpg (in the winter with weight in the bed). These extremes rarely ever happen though, 2 or 3 times each year. I've built an excel spreadsheet for my fuel economy, and it's all right around that 22.8mpg mark.

To improve your economy, you should try putting in a new oxygen sensor (the carbed B2200 models have an O2 sensor to) and a higher flow muffler. I did this and got 15% better mileage. Anything you can do to move intake/exhaust better will improve mileage.

What kind of plugs did you put on? If not NGK, go get some. You can retard your timing a little which is better for highway driving anyway and you won't shift as often, for better terms each gear will last longer. Check that and see.

Well I have a open air cone filter on mine....no idea about exhaust other than a new cat on there....it had to to pass emissions and the previous owner did it before I bought mine....havent checked my plugs but wires looking fairly new...but I am gonna do accel or something along that line and exhaust is in the planning stage....just shoppping for mufflers, etc....will most likely be welded by myself. Again not trying to threadjack, just working so we both can learn, increase, etc......


and for tweaker....my emissions is superlow since the cat replacement....it was horrible B4 as previous had paperwork showing me all that and on everything it dropped to near nothing. I figure maybe a good cap and rotor system and some plugs/wires may help more?

All good tips and comments.
I am going to check my exhaust system.
I dont know much about retarting the timing.
I did use NKG- I was not sold on them until I put some in my girlfriends 99 Accord v6 coup it made a huge difference. So when I bought plugs for the mazda I used the NKG.

I am thinking about doing some seafoam, but my original carb is still working well, it races in the morning on a cold day but once warmed up it idle smoothly so I dont want to mess with it too much.