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  1. #31
    Site Sponsor Dale G's Avatar
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    Quote Originally Posted by fsgarrett View Post
    I have a 2012 F-250 Lariat pulling a 303 RLS, which would be similar in weight. Several years ago I transitioned from a 29 ft bumper pull to the 303 fifth wheel and assumed a different fuel mileage...but it really didn't make much difference. The fifth wheel is much easier to drive in crosswinds and being passed by or meeting semis however. My truck has a 6-speed versus your 10-speed transmission but I average 11+/- wind. I say that because with tailwind I have seen 13 and with headwind as low as 9. As someone else in this chain mentioned, my sweet spot for mileage is 65-67 mph. I usually set my cruise on 65 and may bump up to pass someone on the interstate, then resume 65 mph.

    Good luck with the new trailer.
    That is great to hear. Most of the time I drive 67 to 68 but will do 70 if the traffic and roads allow it, especially on those long stretches of interstate that seem to go on forever. Crossing Kansas or Texas comes to mind.

    Thanks,
    Dale
    Dale & Tammy
    Retired U. S Army and Retired Helicopter Pilot
    2021 Ford F-350, 6.7L Diesel, 4x4, Lariat Ultimate
    2018 Grand Design Imagine 2670MK (sold)
    2022 Grand Design Reflection 337RLS

  2. #32
    Seasoned Camper
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    When asked what kind of mpg I get when towing I usually answer "it's lousy". I remind myself that I bought the rig because we enjoy the RV experience and I knew that there was nothing about ownership that would be inexpensive. I also remind myself that most of my overall fuel consumption from the 4 vehicles that I own are not pulling a trailer. For me, when my truck's fuel tank approaches 1/4 of a tank, I stop and fill it up. I almost never push the button to read fuel consumption anymore. I would rather keep the smile on my face when I'm on road to our next RV adventure.

  3. #33
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    Quote Originally Posted by Dale G View Post
    I have a 2021 Ford F-350 SRW CCSB 4x4 Lariat Ultimate with 3.31 gears and the 6.7 diesel and I am currently towing an Imagine 2670MK, which weighs 8100 when we are fully loaded, and I get in the upper 11’s to lower 12’s towing at 70mph. I am getting 20 to 22 not towing at 70 to 75mph. This winter we are thinking of selling the Imagine and buying a Reflection 337RLS. What kind of towing mileage is everyone getting towing this camper with a similar truck?

    Thanks for the info,
    Dale
    We went out west last year. 5000 miles, up and down mountains, 4 national parks. 3.55 rear end, 10th gear locked out, cruise set at 66mph. 1600 rpms. Trip mileage was 13.4 This truck loves it! Almost never down-shifted. (except going down grades of course)
    Dan and Deb
    2021 337RLS
    2020 Lariat Super Duty 6.7 Diesel Crew Cab Max Tow, Air Lift 5000

  4. #34
    Site Sponsor Dale G's Avatar
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    Quote Originally Posted by RVing in Michigan View Post
    We went out west last year. 5000 miles, up and down mountains, 4 national parks. 3.55 rear end, 10th gear locked out, cruise set at 66mph. 1600 rpms. Trip mileage was 13.4 This truck loves it! Almost never down-shifted. (except going down grades of course)
    That's incredible mileage, even better than I get towing the Imagine. Do you have the 20" tires with the 3.55 rear end or the 18" tires?
    Dale
    Dale & Tammy
    Retired U. S Army and Retired Helicopter Pilot
    2021 Ford F-350, 6.7L Diesel, 4x4, Lariat Ultimate
    2018 Grand Design Imagine 2670MK (sold)
    2022 Grand Design Reflection 337RLS

  5. #35
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    Quote Originally Posted by Dale G View Post
    That's incredible mileage, even better than I get towing the Imagine. Do you have the 20" tires with the 3.55 rear end or the 18" tires?
    Dale
    20" MichelinsClick image for larger version. 

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    Last edited by RVing in Michigan; 09-14-2021 at 01:32 PM.
    Dan and Deb
    2021 337RLS
    2020 Lariat Super Duty 6.7 Diesel Crew Cab Max Tow, Air Lift 5000

  6. #36
    Site Sponsor Dale G's Avatar
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    Quote Originally Posted by RVing in Michigan View Post
    20" MichelinsClick image for larger version. 

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    From what I was able to find out the final drive, where the tire meets the road, is very close to being the same between a truck with the 10 speed, 3.55 gears, and 20" tires and a truck with the 10 speed, 3.31 gears, and 18" tires. I think that is why Ford makes the 3.31 gears standard with 18" tires and the 3.55 gears standard with the 20" tires. So our RPM should almost be identical at the same speed. At 70MPH in 10th mine should turn 1533RPM and yours should be 1548. At 66MPH and 9th gear mine would be 1571 and yours would be 1586. At 67MPH in 9th mine would be 1595 and yours would be 1610. 73MPH in 10th mine would turn 1599 and yours 1614. This is why I get better mileage at 70 to 72 in 10th gear versus 10th gear and 65 to 67. On our next trip I will have to try 9th gear and 67MPH and see what I get.

    If you are interested in playing with the numbers and gears these are the websites. I used the standard 32.1" for 275/65-18s and 34.1" for the 275/65-20s.
    https://www.dieselhub.com/tech/ratio-tool.html
    https://www.dieselhub.com/trans/10r1...qshift-10.html
    This one is good for figuring out tire diameters. http://www.rimsntires.com/specspro.jsp

    Thanks for the information,
    Dale
    Dale & Tammy
    Retired U. S Army and Retired Helicopter Pilot
    2021 Ford F-350, 6.7L Diesel, 4x4, Lariat Ultimate
    2018 Grand Design Imagine 2670MK (sold)
    2022 Grand Design Reflection 337RLS

  7. #37
    Site Sponsor Dale G's Avatar
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    With all of the delays and no guarantees for delivery dates or prices, we have decided to keep the Imagine and do some upgrades to make it nicer. Thanks for all of the information on mileage pulling the 337RLS. I did use my EFS Fuel Card for the first time on our trip from Southeast Missouri to Luray, VA and back. We filled up at only truck stops, was told they have fresher fuel than the smaller stations so better fuel mileage, and I got between 12.1 to 12.5 MPG driving 68 to 70 MPH. I also saved anywhere from $.20 to $.45/gallon off the posted price. This is after all of the charges and fees. What was nice was the final price was even $.10 to $.20/gallon cheaper than the auto filling stations at the same exit. Using the card might be a little more work but it definitely saves money and I get better MPG using the truck stops. When we went out to New Mexico and Arizona this summer we stopped wherever the cheapest fuel was and we got as low as 8.7MPG and could only get in the upper 11's at best.

    Dale
    Dale & Tammy
    Retired U. S Army and Retired Helicopter Pilot
    2021 Ford F-350, 6.7L Diesel, 4x4, Lariat Ultimate
    2018 Grand Design Imagine 2670MK (sold)
    2022 Grand Design Reflection 337RLS

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