Thanks to you guys here I gained 2 mpg in one tank. My truck has been hovering around 9.5 mpgs since I got it. Put a 5-star econo tune on it, and it improved a little bit, but still didn't hit 10 mpg. I went on a trip recently. When I filled up right before I left, I calculated my mileage like I always do and it was down to 9.3 mpg. It's been falling for the last few tanks, and this one was my second worst or so tank of gas yet. I drove about 100 miles, and I had used over a quarter tank of gas, probably about a third. I stopped to get something to drink and I noticed that it seemed to be idling a little rough. I thought, "You know, them boys on the FTE forums mentioned that if the MAF is dirty it'll kill the mpg and idle, and I did just oil my air filter." Went up to the O'Reilly there, got some MAF cleaner and cleaned it. Immediately noticed and increase in power. Next fillup I calculated 11.3 mpgs! Nice.

I think it was Krewat who I saw mention it first, but anyway, thanks for kicking *** FTE.

I also decided to test out the 87 econo and the 87 perf tunes on gas mileage. I used the econo tune on the way up there, and around town for a bit, then switched to the perf tune on a fill up. Drove around town on that tank, then came back on a tank and a quarter. So one tank each is all highway and one tank is city with about 1/4 highway.

Econo:
Highway
344.1 mi, 30.296 gal
11.36 mpg
(this is the tank that got the MAF cleaned about 1/3 of the way through, so it could have been a little better probably.)
City
280.6 mi, 26.659 gal
10.53mpg

Perf:
City
215.7 mi, 20.386 gal
10.59 mpg
(I put the perf tune on about 12 miles into this tank.)

Highway
311.8 mi, 27.142 gal
11.49 mpg

So the perf tune and the econo tune were pretty close on the comparable tanks, with the perf getting very slightly better mileage. I drove pretty consistently with the both of them. Highway 70-75 most of the way. I did use the cruise control a little more on the perf I think.

 

That's awesome! I cleaned my MAF, put in new spark plugs, along with my favorite air filter and fuel additive and now average about 14.5 MPG on the highway. Fortunately I don't hit the freeway much, because the extra 10 MPH costs me about 1 MPG due to my 4.30 gearing.

My best mileage was 17.4 MPG, but only on one tank.

 

Sweet! I was all excited about breakin' 11mpg. What fuel additive do you use?

I just changed the plugs a couple weeks ago. Didn't do the boots, cause they all looked new, and the plugs only looked a couple-three months old. I had started with the plugs, so I changed 'em all anyway, but I probably didn't need to. I actually did change one boot, cause it was lookin' a little dirtier than I wanted, and I put dielectric on all the other boots.

I'm glad I took it all apart though. The PO put on a K&N intake, and he had some funny ideas about how you use washers. He put washers between the gasket and the mating surface on the MAF housing. You could see where air was getting through.

 

Cleaning the MAF is the first thing I do whenever it "doesn't feel right". It effects shifting, gas mileage, throttle response, so much more, and it doesn't hurt anything to clean it.

I too got around 17.2MPG on the highway, ONCE, but usually average 16-16.5 depending on my driving and rest stops.

Around town, I'm still getting only 6.5 but I can't keep my foot out of it

 

That's getting harder for me to do too.
Just put the SPD y pipe on yesterday and boy does that make it sound good! The PO put glasspacks on, and when I got it I thought, "well, that sounds pretty good. Not super growly, but it's got a hint." Now, well, lets just say I like it. Specially after it breaks 2200 rpm and you have your foot in it. What else is nice is that it's not loud and obtrusive while you're just cruising.

 

Oh, and my last tank, with about 3/4 of it in town driving mixed highway/city was even better mileage than the last highway tank! Not sure why, but if it keeps this up, I'm really gonna like it.