My truck 2010 f150 4x4 w 6in lift and 35s 5mpg pulling a trailer
 

Any solutions to my mileage problem. Put a k&n intake on it and borla exhaust to try to combat the fuel mileage loss. It helped initially. Then all of a sudden it started getting 5mpg. Got 151 miles out of 31 gallons of E85. Need help!!

Well, for starters, E85 isn't going to get but aboutn 60-70% of the fuel mileage gas would give you. E85 just doesn't deliver as much energy as non ethanol does. The other thing, pulling with 35s, unless you've regeared, the truck is not working within it's most efficient range for fuel mileage. Thirty-five inch tires effectively raise the gear ratio significantly over stock and increases load on the engine. Plus, you've got a 6" lift, which effectively raises your vehicle and increases wind resistance dramatically. It's not going to get good fuel mileage no matter what you do. Be careful with that K and N, I've personally seen several allow way more dirt through than should be allowed. They don't "add" any power.

Jacked up truck (4x4 no less), big tires, pulling a trailer, and burning ethanol gas. Do the math. It's not any surprise that your fuel economy is terrible. I really doubt the intake and exhaust made much of a measurable improvement, but maybe a little. As mentioned above, the K&N air filter is not a very good filter. I used to use them until I started to notice a fine dust coating in the intake tube of a 7.3 diesel I had. That was the immediate end of me using K&N filters. I now use OEM or Donaldson. Neither one is cheap, but neither is an engine.

[QUOTE=eng208;5844694]Well, for starters, E85 isn't going to get but about 60-70% of the fuel mileage gas would give you. E85 just doesn't deliver as much energy as non ethanol does. The other thing, pulling with 35s, unless you've regeared, the truck is not working within it's most efficient range for fuel mileage. Thirty-five inch tires effectively raise the gear ratio significantly over stock and increases load on the engine. Plus, you've got a 6" lift, which effectively raises your vehicle and increases wind resistance dramatically. It's not going to get good fuel mileage no matter what you do. Be careful with that K and N, I've personally seen several allow way more dirt through than should be allowed. They don't "add" any power.[/QUO

I knew the mileage would not be very good, just didn't think about the E85 causing it to suck that bad!! All I saw was it was about 30 or 40 cents cheaper. I wont be using it anymore. Should the truck be regeared and calibrated for the bigger tires???

Your gauges will all be incorrect, including mpg, unless you reprogram it for larger tires. Regearing would help your power band, but that is more about how you want the truck to drive than mpg.

E85 dropped me from 16mpg to 12.5 when I used it for a month. Just normal road/highway driving.

[QUOTE=Kmck;5847078]Re-Gearing would put the "sweet spot" back where it should be with bigger tires.

FWIW, I towed a 6500# travel trailer 4k miles last year with my truck. Not lifted, factory size tires (change to LT from P-Metric); I got about 7-8mpg the entire trip @60-70mph.

I did make the mistake of running 87 octane while towing on that trip. Truck definitely prefers 91 octane when towing; I see better mpg - I just haven't towed that heavy/long since that trip to really document changes.

What tire size was on the pickup before hand? 32"? 31?

If it's 31", 35" is 13% taller, so you're going 13% faster than you think you are, and covering that much more ground. That only accounts for <1MPG at 5, but is part of it.

To account for 0% ethanol vs E85, you're only getting 66.6% of the energy of regular gas. That puts you at 8.5 MPG. Still factoring in the 35's vs. 31's math. Curious what engine RPM's you're turning and at what speeds you're driving. 6" lift kit is going to be like pulling a parachute, but if it's what you want, just going to have to pony up at the pump lol.