Well, just got my first tank of ULSD ran thru the Blue Bird Bus.

The overhead said 15.7 avg mpg......hand calculated, it ended up being 14.6 mpg.

I'll give it a second fill-up before I decide if it's to be or not. I'm quite sure the dealer didn't fill it up the way I normally do. My best fuel economy didn't hit until around 20k miles on my past three CTD's, too.....I think I need to throw the wife's JEEP Liberty on the car hauler and find some hills to accelerate break-in.

462.3 miles / 31.683 gals = 14.6 mpg.

462.3 miles and 11:52 = 38.957 avg mph.

Casper could always easily go 550+ miles before the low fuel light came on.

Greg

 

I hope it gets better, i've got 30k on mine and still getting that kind of mileage. IT SUX!!!!

 

i've resigned myself to accept that the 6.7's will lose about 1.5-2 mpg to the dp-filter and the bigger motor, and about another 1 or so to the ulsd..... our 03 7.3 which has seen 21 is averaging about one less than we're accustomed to. 4500 miles and averaging 14.5 mixed driving.

 

My first tank also ave. 14.5 ,hand calc, checked next one and got 15.5. Several fillups later still at 15.5 for around town driving. The overhead computer on mine reads about 3/4 mpg higher than hand calc.
Will be pulling 11m lbs. next week , be interested in calculating that.

 

Just towed 14K fifth wheel 2,000 miles and mileage hovers right about 10.0, both on the computer and hand calculated. Not towing (measured over 700 miles) averaged 14.5 indicated and measured.

 

Well I just towed my 13k triple axle toy hauler coast to coast and back (7100 miles round trip) at 68-75 mph and and got 8.5 average. I just changed the fuel filter to see if it helps with milage. It has 10600 miles now. I haven't had a single problem with mine, other than crappy milage. I wish I would have kept my 03 and air bagged it. Don't get me wrong, it tows great but my 03 got 3 mpg better towing and 6 mpg empty. Not the exactly the same truck ie single/3.73/nv5600 vs the new one. If it don't get better, this one is going to get sold. So start saving your pennies.

I wouldn't be so ****** if my brother wasn't getting 7-7.2 with his KENWORTH, loaded!

 

man that sux i have heard u need to wait until 20-30k for the mileage to relly improve
i test drove the new 07 6/7 and they are just amazing
except it had 27miles on it which on the overhead screen said 10-11 city
i didnt hit the highway
man these things are exspensive!!

 

You need to give it time to loosen up a bit. I know it's going to ruin your day everytime you fill up, but give it time and you won't be able to wipe the smile off your face. My dad's 04.5 was the same way, it consistently got 14 MPG for the first 20 or 30 thousand miles. Then it slowly kept creeping up and now he's getting 19-20 consistently. 16.6 while towing 6K.

If you sell it, someone else is just going to reap all the benefits. Then again, maybe used is the way to go. Let someone else take the financial hit of driving off the dealer lot, and also let them break it in for you...

 

ughh, this pretty much clinches it. I'm keeping my 5.9 running until (if) I need more carrying capacity - then either putting Ricksons on it or trading it for a 5.9 dually. Too bad with all this talk about better for the environment the new stuff burns sooo much more fuel.

 

Man that is bad mileage, I'll probably get that towing a 5ver at 12k. Now those 6 spd seem to rock, time will tell on longevity.

 

I've ahd my 6.7 4 1/2 days now and according to the computer, 15.4 and this is pretty steady. We'll see after 10,000 if there is a difference,

 

i feel for you guys.......I agree with one of the posts above about it supposedly being better for the environment. yea less emissions are put out by the truck, but its using alot more fuel now. another thing to think about it that refinery's are having to produce more diesel because of more demand. So they create more emissions trying to refine product into diesel.

something just dont seem logical about that!!!

 

Fuel mileage is all about load, speed, and wind resistance.

I get 14 MPG consistently in the crappy stop-and-go traffic around here, but get me out on a country road with a 55 MPH speed limit and no lights, and I'm getting over 20 MPG.

The MPG figure in question as a weighted average. The more time spent getting 5-7 MPG accelerating, the worse it will be. The more time spent in steady-state low speed crusing (40-55 MPH), the closer to 21 MPG you will get.

Each stop light takes its toll in fuel. Thank your city planners, not your trucks, for the horrible fuel mileage.

Before I get any rebuttals about bad MPG at freeway speed, wind resistance picks up quite a bit over 55 MPH, and your crappy economy is due to driving too fast. I am quite often the only guy on the freeway driving the speed limit, but my overhead usually reads 19.5-20 at 65 MPH, which means 18-18.5MPG. On country roads I have achieved a solid 21 MPG with a tailwind, or 20-21 on flats, steady state cruising.

Use cruise control, don't hit stop lights, stay at low speeds. Your economy will be great.