Gas mileage

We have a 2005 GMC Envoy XL with the straight 6 cylinder engine. When not towing, we get 16-18 mpg. When towing the 177, we get 11 on moderately flat ground and 8-10 in hilly/mountainous areas. And that's strictly when we're actually towing.

From my experience, speed when towing is what destroys your mileage. Going 65 mph drops our mileage by around 20%. Going 55 instead of 60 improves our mileage by about 10%; I've never tried 50 mph. But my wife isn't very patient, so we compromise and travel at 60 mph on the highway.

The best mileage I've personally heard anyone getting was a guy pulling a Pod with a GMC 3500 diesel. He got 14 on the highway when towing, but his mileage remained practically the same even when he wasn't towing, so that doesn't seem like a good solution either.

If you're getting 13 or better strictly when towing, be very happy. And remember, you didn't buy your Pod to improve your fuel efficiency; it improves your happiness factor.

My maiden voyage with our 177 was a couple of weeks ago, towing 660 miles from Omaha to Colorado with a 2004 Durango (4.7 liter V-8).  Averaged about 11 mpg, driving about 65 mph or a bit more, with a moderate cross- or headwind most of the way.  Can't see myself driving much slower than that, so I'm prepared to grin and bear it (and pray for sub-$3/gallon gas to return!).

From central coast of California to Yellowstone and back..got 14 mpg towing 179 with 2001 f350 power stroke keeping it at 1900 rpms.....67 mph...pretty stoked, but a total of 3200 miles was still a lot of $. !!!  Still beats a hotel room without a view driving a Prius...... !!!!!!!

Originally posted by Norsk1 Trailer did well but the Ford limped home. For the weight of the trailer it seems like we would have had better gas mileage. Also the speed limits were 50 to 60 miles per hour or lower. Ron

Please elaborate on the "Ford limped home" part.   I've been curious about the different EcoBoost engine's performance and mileage, especially with the class action lawsuit about the 3.5L EcoBoost problems. 
Before I retired in June I put 30,000 miles on a Ford Ecoboost Escape AWD with the 1.6L engine.
Very impressive performance for such a small engine.  However gas mileage was never anywhere near what Ford claims, something like 32mpg. 
Never saw over 25 and even that was rare, usually around 22/23.

The ford limped home in a mode where it shuts off air and reduces speed and shifting function. This started after entering Alaska at Tok. We drove in heavy rain from took to Denali. The ford started by acting like it was misfiring in 6th gear. I switched to premium fuel while in Alaska.
On our return we left Tok in a torrential down pour and soon hit road construction where mud and potholes were pretty bad. It was during this 20 mile stretch when the ford wrench indicator came on with a check engine light. We then went into the limp mode. Then on highway 37 in a heavy rain I was going to pass a small trailer and suv. The ford almost died and I realized how limited this mode is. After being home for 3 days in dry weather the wrench indicator left and the check engine light went away. I have an appointment Tuesday to check if anything can be found. I made a trip to town yesterday (200 miles)to pick up mu lab and all went well except for a little 6th gear misfire.
Ron