5.9 vs 6.7 mileage

[bheiting]

My overhead is fairly accurate. If I keep the speed under 60mph I can get 21mpg - truck empty. With my 1200 lb truck camper, I get 17-18 mpg at 65mph.

 

[HBarlow]

My overhead is fairly accurate. If I keep the speed under 60mph I can get 21mpg - truck empty. With my 1200 lb truck camper, I get 17-18 mpg at 65mph.

Good. Your numbers are similar to what I've been seeing.

I don't think that these new ISB6. 7s are as bad on fuel as some think.

 

[MChrist]

Smarty must really mess with my OLM then. My best tank to date gave me 21. 3 hand calculated, 65 mph, mostly highway. OLM said 28. 7!! I've had 4 tanks that did over 20 mpg hand calculated. I've never had the patience to drive 10 hours at 55, but I would like to believe I could hit 23...

 

[98ramtough]

I had a 2007 5. 9 that I used to average 18 with. Highway at 70mph on a trip I would average 21mpg. This was with taller tires and a canopy. Not sure if either helps.



On my 2010 I am currently running 285/75/17 toyo tires that measure 34 inches tall. I can say that on my 2010 the taller tires hurt the mileage. On my 2007 taller tires helped. Both trucks had the 3. 73 gears.



My 2010 average with EGR unplugged is 15. 5. All highway it is 16. 5. EGR Plugged in is about 1mpg difference. Mileage sucks on the new trucks. Plain and simple. Great power, awesome comfort and interior, but the mileage SUCKS big, sweaty, stinky, furry... You get it.



Don't get me wrong, I do love my 2010, my wife drives it and loves it. I, myself and partial to the 5. 9s. Cheaper to work on, cheaper to run, cheaper to fix. That is why I just bought a 12 valve.



Oh yeah, my 2010 towing my new truck 200 miles with a total weight I would guess at around 11k lbs got 9. 8 mpg and had plenty of power to pull up hills and stopped GREAT with the exhaust break.



You gotto pay to play. Everything has a trade off.

 

[rscurtis]

Smarty must really mess with my OLM then. My best tank to date gave me 21. 3 hand calculated, 65 mph, mostly highway. OLM said 28. 7!! I've had 4 tanks that did over 20 mpg hand calculated. I've never had the patience to drive 10 hours at 55, but I would like to believe I could hit 23...

At 55, I could probably approach 30 MPG. Too bad there's no practical way to try it.

 

[sag2]

OK, my memory is not as good as it used to be. Pulled the spreadsheet for the trip and average was 8. 4 MPG with a low of 6. 8 and high of 10. 4. Four tanks in the low 9's, three in the low 10's. The lowest tank was coming home from Heber City UT to Wells NV. I have to assume we were pulling a pretty good head wind all the way across the salt flats, and then it is a long pull from Wendover into wells. Sorry for the error. It's amazing looking at the numbers that the one low tank pulled the average to 8. 4 with seven tanks at 9+.

 

[MChrist]

Sag2, on the trip when you got your 6. 8 mpg tank towing heavy and at 75, I imagine you were in O/D? That probably puts you around 2000 rpm, which is a pretty good sweet spot, depending on gearing. I believe you, I'm just surprised, that's all. Never heard a number that low. Most of my towing is pretty flat terrain.

 

[sag2]

It depended on who was driving. If it was me it was in OD, if it was my neighbor, tow/haul on and possibly OD off. The pull from Wendover to Wells is pretty good, and some years the wind has been blowing like crazy. We never seem to hit the tail winds, always head wind. In fact we have run out of fuel twice since 2000 because the wind started blowing and the mileage went down. Luck we are always carrying fuel with us.

 

[MChrist]

Thanks for the detailed info. There must be some sick, twisted part of me that WANTS to tow heavy, uphill, and against wind. I'm always looking for ways to make that Cummins earn it's keep! Living in the flatlands doesn't help, though.