Towing Fuel Mileage

[JohnnyR]

2012 Duramax 3500HD. towing a 3 axle 5th whl toyhauler weighing 16K with inside contents. Getting 7.5 to 8 mpg running 65 to 70 mph. seems low compared to my previous Duramaxes,admittedly with less load. What is everyone else getting?

[paoutdoorsman]

I assume you have a large frontal area on that 5'ver? I took a buddies 2012 F350 with 35 open goose neck on a 1400 mile loop up the Canadian border, back down around through Vermont, and back accross New York over Thanksgiving weekend. I added frieght at 3 different stops along the way. Once I was loaded, it was comparable to what you're seeing. It would pull around 9 mpg on the flatter stuff, but dropped to mid 8's once I hit some more hilly terrain. I was at 22-23K gross, but with less frontal area than what you have I'm sure.

[richp]

Hi,

My '09 tows my roughly 12.5k fiver at 60-65 yielding about 10 mpg, depending on outside temperature, wind and terrain.

Over the years, I've concluded frontal area (huge in my case) and speed (moderate in my case) make the biggest difference in fuel consumption. If you're going that fast, I think your figures are pretty good.

FWIW.

[Mark Rinker]

Try 62mph cruising speed for three tankfuls - calculate the $$$ savings.

[Roy W]

Mark's got it. Hold it at 2000 rpm.

[Mark Rinker]

Actually in 6th gear, 62mph should be under 2000, but yes 1800-2000 is a good cruise target for maximum mileage, loaded.

If wind drag is large factor, then the slower the better, within reason. 58mph sure saves a lot of fuel.

I equate it to this: Get up earlier in the morning, stay in the saddle a little longer in the afternoon, get to bed a little earlier. Makes a traveler healthier, wealthier, and wiser...;)

[JohnnyR]

Thx for the responses. Makes me feel better. As Mark said, 2000 RPM is 70 mph in 6th gear. Ran a lot of this trip from TX to CA in 5th gear at 65 mph due to hills and wind. Guess what really upset me was that I talked with a guy at one of the stops with a new Ford 6.7L F450 CC dually pulling a high end heavy 5er, aupposedly 21K lbs, who told me he was getting 13.5 mpg. Personally I don't think he knew what he was talking about or he was just jerking my chain, but it stuck in my mind. Made me wonder if I should have bought a Ford. Anyway, guess I need to slow down some and see what happens.

[CoyleJR]

Mark is correct about getting the best fuel mileage running around 62mph. With my 06 LBZ pulling a 38' 5th wheel and a total weight more than 24k # I often get around 12mpg. The sweet spot for fuel mileage with my truck is 58-62 mph. Any faster than 62mph and the wind resistance increases drastically and the mpg drops big time.

John

[JohnnyR]

Mark,CoyleJR
What RPM are you turning at 58-62 mph? With the 5 spd, I would say 1800 or so. But I see one of you has 19.5 inch wheels.

[CoyleJR]

JohnnyR,

With the 19.5 tires the RPMs are 1700 to 1900. On my truck 1750 to 1800 gets me the best mpg. Additionally, on the hills I am the guy in the slow lane with the flashers on going 30-35 keeping the EGT and fuel consumption down. I am often passed by rigs similar to mine going 60mph on the same grade. I suspect they use 10 gallons of fuel on a hill that I use 1 or 2 gallons to climb.

John

[JohnnyR]

Yep, gonna have to be a little more judicious on the throttle when pulling this 41 ft toyhauler vs the previous 32 ft 5er. Thx again for the replies.

[gimpyhauler]

Does anyone but me just hit the cruise when I start and enjoy the ride? I just returned from CA to OR and back and set the cruise at 62. I could save by setting it lower but it just doesn't seem worth it when all the Semis are passing me.