Hey,
I just bought a 97 F250 LD, Ext Cab, 4x4 Lariat, I love the truck. It's a bright red/silver with the 285x75x16's on it. I'm wondering what I can do to improve the mileage slightly. I've been averaging right at 14 using 89 octane with it. I'm not sure if the speedo has been recalibrated for the bigger tires or not. Any ideas on mods I could do to raise the mileage slightly? I love the truck, I just want to make sure I don't put all my money into gas and not my payment!
Thanks

 

The best two things you could do is to put in a K&N air filter, and to put on a tonneau cover. With my 4.6l I get 18-19 on the highway. Hope this helps.

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99 F150, 4x4, SC, ORP, 3.55, 4.6l, auto

 

Get a good cat-back system. I just bought a Flowmaster 50 series cat-back system for about $300 with the Chrome tips and installation. I've already noticed a significant boost in mileage. I'd say I'm actually getting about 22 on the highway. It's great! And it sounds good too!

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1998 F-150 Lariat SC
Toreador Red w/ Harvest Gold Trim around bottom
5.4L SOHC Triton V-8
K&N Filtercharger
4x4; 3.55 LS; Off Road Pkg.; 17" wheels; 4x4 shifter ON THE FLOOR WHERE IT SHOULD BE
Bridgestone Dueler AT/S
Chrome Brush Guard w/2 Pilot 55w halogen driving lights
Chrome Double/Single Roll bar w/4 100w Eagle Eye Off road lights
Ford Insignia mud flaps
Flowmaster Cat-Back Duals w/2 chamber mufflers
GTS Headlight & Taillight Covers
Ventvisors
Hella Dual Trumpet horns
6-disc CD changer
Red interior lights
Uniden 40 Ch. CB Radio
"Her name is Jasmine!"

 

WOW! So are you guessing on this or are you actually getting 22? If it's true you need to have your truck inspected by Ford because that is incredible with the setup you have.

 

A good catback isn't going to improve your mileage that much. It is more than likely that the K&N made most of the difference. I had one installed about a month before adding a Borla catback. I had been keeping records since my first tank of gas last August. Until I added the K&N, I was averaging 16.5 mpg (combo hwy and city driving) on my 5.4L. After the intake upgrade and time for the computer to "catch up", I averaged 17.8mpg. Exactly 45 days later, I added the Borla. After another month I re-tallied the numbers and have consistently averaged 18.5mpg.
Next mod.......A tonneau. That should give me another mile per gallon, at least.

 

The FIPK, cat-back, and Superchip combined with a year of mileage checks rarily yield 1 mpg improvements on my truck; 14 city/17 highway.

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2000 F-150 XL, RC, LB, 5.4L, 4R70W, 4.10LS,
Class III tow, Payload #3, & Convenience pkgs.,
4-wheel disc/ABS, Chestnut/Parchment 40/60,
Ford bedliner w/Paintsaver & gas/wheel/spare locks,
K&N F.I.P.K. w/Outwears pre-filter, Superchip,
Dynomax ultra-flow welded 3" cat-back w/ 3" Y-pipe,
Hellwig front & rear anti-sway bars, Rancho RS 9000s,
Pirelli Scorpion Zero 275/60/16s, Mobil 1, K&N oil filter.

 

It must be down hill both ways if you are getting 22 mpg with a 5.4 4x4!

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2001 F-150 SuperCrew Lariat 4x4 5.4L
2000 Suburban LT 4x4 5.3L
2000 Honda RC51
1999 Mustang GT Convertible