I have a 2010 SCREW 5.4 w/3.55 rear end less than 3k miles. I purchased a 21' travel trailer w/an 8' deck in front to haul my Harley. I picked up the trailer in Ohio drove 155 miles and averaged 6 mpg driving at 72mph and 2200-2300rpm. I want to visit family in Texas, but need better mpg to do it. I did install a Bully Dog GT Tuner before picking up the trailer, don't know if it helped or not.

 

that is horrible milage for a small trailer. I can put my V-max in the bed of my truck and pull a 25' Travel Trailer and still get 10-12 on the highway! The killer is going up any long grades. There is about a 3-5 mile grade on the northeast extension of the pa turnpike that kills mileage. I would try to keep it close to the 2k rpms and slow down.....that will help a lot.

Jim

 

Just tow'd a 14x7 tandom axle trailer full of gasoline/chemical/cleaning products, and lawn mower,snow blower, pressure washer, guns/amo, and any other items you can thank of that the moving van wouldn't take in my move to our new house some 675 miles away. Pulled the trailer with my 2009 Lariat SCREW with the same 5.4 and 3.55s in the rearend. I got right at 12.5 mpg running just under 2000 RPM, and staying right around 70 mph or a little less. I used 87 octane gas, and kept it in "Towing Mode". I agree with Jim, as I think the key is in the right foots. Keep the RPMs @ 2000 or lower, and speed less then 70 MPH. You'd be suprised what would result if you slowed down to 65 MPH! $7.00 gas will lighten up a lot of RIGHT FEET! JOHNWAYNE

 

I would uninstall the tuner and try again.

 

Get rid of the Bully Dog. The only programmers that really work right on the 2009+ are SCT devices.

 

Try slowing down for better mpg's.

 

Your TT tires are only rated for 65mph. Slow down and you'll go up to 8mpg. You also might want to go down a gear and spin 2500-2700rpm. More torque available, less accelerator pedal, better fuel economy.

Single digit TT towing is common for gas engines. It isn't the weight as much as the 8x8' wall you are pulling through the air.

 

That's not normal for a 5.4 with a little trailer. I tow a 30' tandem axle boat trailer (~5000 lbs loaded down) and average 12 towing. 2009 FX4, so I have a 5.4 with 3.73 axle. Even against a strong head wind, I won't get worse than 10 mpg. My 2002 used to get around 8 mpg towing the same boat. Try it without the programmer.

 

A Boat is a lot more aerodynamic than a travel trailer RV. 6-8mpg is very common at 65mph for gas engines towing RVs.

 

How do you go down a gear in an 09 or 10 since the only way to change gears is the gear leaver and move it to 3rd which would be turning 3000+? 09's don't have the Select shift trannies that the 11's do. I have a 2010 and in Tow Haul mode you are at the mercy of the trannies programer. It goes in what ever gear it wants.

 

I got around 8 mpg with my trailer i pulled with mixed grade levels. 3:73 with 5.4l. 2010 fx4. I think its 16 ft. its my uncles stock trailer and i was loaded to the brim with crap in the bed and trailer. I also ran around 70mph give or take a few.

 

You keep at those speeds and you'll have a tire bow out. RV tires are only rated at 65 mph and that's even questionable. I drive at 60 mph and never had problems. My cousin had the same camper and drove in the 70s, he had several blowouts in the couple years he owned his.

The answer to better MPG while towing an RV is keep all the tires at max air pressure, keep your air filter changed, every 2 oil changes (~10,000 - 15,000 miles), and drive 55 mph to 60 mph.

I towed my 22.5' full weight, full height Jayco Jay Flight Travel Trailer with my 2008 Explorer Sport Trac with a 4.6L 3 valve V8 and the 6 speed transmission and got ~9 mpg to 9.5 mpg. See that tall wall right behind my truck? My mileage dropped significantly when there were head or side winds, low tire pressure on the truck or trailer, drove over 60 mph, or had moderately dirty air filter or dirty fuel filter. I've dropped down to 7 mpg when these 2 or 3 of the above conditions existed.

I'm expecting at least 1 mpg better since the F150 is a taller and wider truck to help with the tall/wide profile of my travel trailer, the F150 has an engine with a lot more torque so that the truck doesn't struggle as much (more so than the 2008 and below 5.4L w/ lousy 4 speed trans and even the 5.0L that the test drive proved weaker), and the F150 engine is more fuel efficient putting out more power and using less gas.

It also sounds like you didn't have the tow haul mode activated and instead put the truck in 3 gear. OR perhaps your electric brakes are dragging.

You definitely have a considerable problem and troubleshooting needs to be done.

 

Mike Up
I actually gained 2mpg when I upgraded from an 06 Frontier V6 AT to an 08 F150 5.4 3.73 with a canopy towing the same TT. Although the TT was only 7'6"Wx9'9"H and weight 4050lbs. Took less gas pedal to pull the same load. I averaged 10-10.5mpg, didn't matter wether it was the mtns @55-60mph or the freeway @65mpg. Now I have taken a step back with a 7200lb TT and our 2010 F150, have only done short (200mile rt) trips but it seems like we are in the 8-9mpg range. Normal I suppose.

 

I would get 9-11 pulling 9k lb boat and trailer no matter where I went. 6 is horrible!

 

I'm getting 14.6 in city and 18 @ 60 with my 2011 5.0 towing around 2800-3000 lbs. Can't say I miss the 5.4, it could not maintain the same speeds on the same roads my 5.0 holds in top gear without dropping a gear. Much better low end torque!