[Carl n Susan]

I too have a 2011 F350 Crew Cab Longbed SRW and I sure didn't see a noticeable increase in MPG once I went past 20K miles. We just returned from two months of traveling covering 5,000 miles (2800 miles towing). We broke 20K about halfway through the trip. Mileage hasn't changed. 9.5 to 11.8 towing depending on speed, hills and wind. Non-towing is harder to pin point as usually a portion of each tank was used to tow. And the other non-towing use was basically in-town at 15-17 MPG.

I record every fill up. The Ford display consistently shows .5 to .9 fewer gallons of fuel than what the pump supplies. You can quibble about the pump values due to foaming, fill rate, temperature, etc, but over time the gallons used are *ALWAYS* less than what the pump delivers. But this is my towing experience. I recently made a 1500 miles trip without the trailer and predominantly on the Interstate Highway. To my amazement, the Ford measured gallons matched the pump! But for our latest trip, things returned to "normal" with a extra 1/2 gallon from the pump each tankful.

Don't get me wrong, I love this truck! It tows wonderfully with power, torque, and mileage that far exceeds my previous 6.4, 6.0, and even 7.3 rides. None of the previous trucks towed my 3700RL (similar in weight to your 3400RL). They hauled my 2955RL at 3,500 lbs, less weight. Yet this truck gets better mileage with less strain than any of the others.