My BFG AT's are class C. I run them at 50 but you can run them at 60. That would help. My vans tires are class E I run them at 70 but they'll hold 80. Like Labnerd said read the tire pressure rating. Truck tires hold allot more air then passenger car tires.

 

I know my BFGs are a LT 265-70R17...I gotta go see what else it says as far as class goes. I know it did say 50PSI Max on the sidewall. Run them at 45?---DirtySCREW

 

Your mileage will be bad right after disconnecting battery or resetting computer because it starts at default settings and has to relearn everything. Yes try 45 psi on those tires. Definitely change the axle seals when you change your fluid. When they leak you will end up needing a brake job because the parking brake drum will get coated with gear oil. I had mine done last year. I am now at 138K miles.

 

Certain tires CAN hold more air pressure, but you have to air your tires according to the load. Too much air and your tires will cup and wear out too soon. Seen it happen and replacing 35" A/T's at 25k couldn't have been pleasant.

 

When you slow down, the difference in wind resistance will have more of a factor than the lower RPM's. My V-6 manual gets its best mileage at 55, I've seen 23+. At 75, the best I've seen is 18 and it's been as bad as 15 with a headwind. You may be able to optimize your mileage with different bed treatments - open with tailgate off, tonneau, full cap. I know what Mythbusters says, but different people have different results.

 

^^^ exactly. In a controlled environment it's one thing. But optimal rpms are not as much of a factor. Usually the best mpg's for us are 45-55 because we are in overdrive. I do well at 40-45 in OD

 

Right, I don't think to many realize that lol.

 

Ok guys, I'll try the 65 MPH on the highway when I go hunting again. My hunting spot is about 45 miles up the road (one way). And I'll try the 45 PSI in the tires. And I'll just hang in there I guess. It's just discouraging to not see any improvements and actually a decrease when you're spending hard earned money to try and IMPROVE mileage and say some $$ in the long run over the life of the truck.
I also just put a bottle of Techron in to see if that would help. That Gumout w/ Regane didn't do anything for me and I know a lot of forums that swear by Techron and thats ALL they use for FI cleaner.
I'm also gonna try and locate some stock TB bolts and take that space off to see if that helps any. There's some of you that are completely stock that are getting better mileage, so it can't hurt.

I'm gonna try and find that Axle seal thread...but what does it cost roughly?
Is it possible that replaceing the axle seals I eliminate SOME friction by worn parts or not greased enough parts that it provides less resistence and in turn its easier on the engine thus yielding slightly better Mpgs (.1-.2)? Or am I grabbing at straws here?

I just don't understand how some are getting 15 city and a little over 18 highway. I guess if I could get her to that I would be somewhat satisfied.

Oh, yea...I gotta go measure my air filter and order a new one. as its dirty. BUt I don't see how a slightly dirty air filter is gonna give me 2-3 MPGs.---DirtySCREW

 

Don't inflate the tires any higher than the max pressure on the sidewall. If they are aggressive tread AT tires, your mileage will be less as the open blocks cause more rolling resistance.

Some vehicles just don't get good gas mileage for no apparent reason. It happens. My son in law has a 98 Scab 4x4 with the offroad package and a 4.6 with 3.55 LS gears. The best he's seen on the highway is 15 on E-10 cruising at around 65, level ground, cruise control. Others with an identical truck may be getting close to 20.

 

DS- In all honesty, I don't think the people that tell you they're getting 3 MPG less in town than on the road are paying much attention or are not very good at math. I have never gotten as little as 3 MPG difference on ANY truck I've owned , and I've owned quite a few. I doubt that axle seals and such are gonna make any difference. There are some vehicles that just never get the mileage that identical vehicles get. Why??? Duknow! More tire pressure (never beyond max!)= less rolling resistance= better milage. Different tires have different rolling resistance. I believe it's Tire Rack's site that has rolling resistance figures, not sure. Synthetic lube in all moving part areas helps, enough to give "worth the cost" improvement? I don't know. Dirty air filter? Not good. My '02 with 4.6 got about 30-35 miles more on a tank (same tank) than my '99 with 5.4. I run a Scangauge II on my '04 5.4 3V and it seems to be very accurate and you can SEE instantaneous as well as average (as well as a whole lot more), no kidding yourself (or anyone else)! I can get 20 + (maybe .2 or.3) on level road with no wind and absolutely steady throttle at 70-75 MPH. (unrealistic conditions) All 3 of my last 3 trucks have had tow pkg. W/3.73 rear axle. Around town - about 10 MPG. That tank takes a lot to get moving and you're not gonna get good around town mileage unless you have a long way between stop lights. (like a few miles ) I don't like the kind of mileage I get in combined driving (not good!), but I haven't been without a truck since '69 and don't want to start now.

 

Variables = there's to many when it comes to mileage, most just don't know lol.

Well I've attacked most as far as hardware and nice clean sensor operation, even Amsoiled the drive train. Now I get some strange numbers, like 16/16, -wtf ? But that 16 highway is @ about 78 mph on cruise.

Oh well, I can live with it. I'm not screwin with it anymore... Honest!

 

Your truck has been regeard. When I had 3:55 I would be around 1700 to 1800 rpm at 70 mph and I had the exact same tires as you. Now with my 4:10 im around 2100 rpm. If you can get LT header I would go for them. Before my LT I would never get more then 265 miles out of a tank of gas. Now im getting atleast 285 to a tank and that is with me driving like a retard listening to the exhaust.

 

I would look at your door for the proper tire pressure reading, if my memory is correct i thinks its 35 all around. And FYI, ford has a billzion tire size for the 150s and such. The door should also say what the proper tire size is from the factory unless the door has been replaced.

 

The door tag is irrelevant if a guy has replaced the tires with after market LT type tires. Most of these trucks come with P type tires that only hold 35 PSI. Nearly ALL LT type tires hold at least 50 PSI. Read the tire side wall.