With almost 800 miles on mine i have been getting between 23 and 24 on the highway with cruise control at 70mph. At night i can get almost 25 when the a/c is turned off and just running vent.

Ive still been told atleast 1000miles before the motor is fully broken in. Some people ive talked too have said there 6.4's they got the best milage at the 2500mile point.

So i guess in a month or 2 i will see if i can manage 25+@70mph

 

The question was why can't these trucks get good mpgs.

The 6.0 and 6.4 were never known for mpgs.

So, if you read, my HP/torque comparison was with the older diesels, circa mid/late 1990. These engines did produce max. torque at around 1600 rpm.

You cannot disconnect the two, they are related:

Power (hp) = Torque (ft-lb) * RPM / 5252

Ultimately, what you ask us to believe, is that at a constant speed, a truck should get the same mpgs no matter what the motor.

 

Gentlemen,

No one is suggesting that mileage depends on engine rpms, are they? Remember that an engine can be turning 2500 rpms coasting downhill or turning 2500 rpms burning up the canyon with a trailer behind. While coasting the engine is producing almost no hp/torque. Push down on the accelerator and you start burning fuel and producing hp/torque. Same rpms, very different mpg.

Ford has added a very cool "instant mpg" feature on the new dash display. It appears as a green bar right next to the trip mileage which indicates the load on the engine. Lot's of green means really good mileage. No green means bad mileage.

As was stated above, you must factor in load and rpms when thinking about mpgs.

 

thats there to make you feel good,and in hopes most people will talk about the fuel mileage their getting with the new diesel based on that meter rather than a few tanks actually calculated.don't be tricked.

 

Yup, you're dead on with the relationship between HP and torque. Kind of cool because I've beaten that subject to death over the last few years and I've grown tired of it.

EpicCowlick got the gist of what I've been trying to say. Engine load varies depending on the driving conditions, and power output varies with engine load. Because of this peak HP or TQ figures are irrelevant when we're talking about cruising fuel economy with a diesel engine.

This is true if the efficiency is the same between the engines. This is the problem we have! Efficiency didn't drop because of HP increases, it dropped because of the measures taken that were required to meet EPA and CARB emissions regulations.

The output of the 7.3L went from 235 to 250 HP in either 2001 or 2002, have you ever heard of one of them complaining about the MPG loss between years? Not likely, simply because there was nothing done to the motor that would hinder efficiency.

I know that spartan tuned 6.4L engines running the high horsepower tunes, which have also had the emissions controls disabled, are getting phenomenal MPGs compared to the rest of us. And we're talking about 650 HP trucks!

The principle is further demonstrated by folks like radzer0 who have the most power PSD ever made! Because it was designed with SCR emissions reduction technology it requires less EGR and they can advance the injection timing. Both of these things vastly increase operating efficiency, but could not be done without SCR technology which enables these engines to meet the emissions limits set by the EPA.

So I'll say it again:

Power output has nothing to do with it!

 

If i was a mechanical engineer i could explain what i know in my head. But i dont know the proper terms.

A good example would be the cadilac CTS engines. In 2009 they had both a Direct injection and a normal one. In 2010 they have only direct injecton. It has an extra 8hp. But gets 2-3mpg better on the highway.

In theory, the current 6.7L PSD at 100% efficency on the power of the fuel. COULD get over 100mpg on the highway. Will that ever happen? Maybe in 50-100 years. But its something like 90% of the energy that could be used to push us forward with our fuel gets dumped into heat and wasted.

Im sure alot of you guys know alot more on this topic than I do. So feel free to try to clarify, english writing skills was never a good topic for me.

 

Ford didn't put that feature in to trick anyone. It is not a gimmick. I simply shows the load on the engine much like the old vacuum gauges used to do. My dad installed one on my old Toyota when I was in high school and taught me how to use it. When I pressed down on the accelerator, the vacuum on the engine would increase and the gauge showed it. I learned how to "feather" the gas pedal to significantly improve my mpgs on that old import. I think it's awesome that Ford brought that back and placed it right in front of the drivers who care. The hyper-milers will go nuts over that.

 

All things being equal that is true, but all things are not equal these days.

You are comparing a new engine to a design that is over a decade old, and technology has changed...... a lot. More efficient and precise engine management, improved combustion chamber designs, improved fuel injection, and improved turbocharger technology (just to name a few) allow for making more power on the same amount of fuel. It's a little thing called thermal efficiency, and newer engines have a big leg up on older ones in this area.

Your old 7.3L while a good engine, and efficient for it's time, couldn't burn fuel as efficiently as say a new 6.7L. In other words the old motor can not produce the same amount of heat energy (and use it) as a newer design given the same amount of fuel.

Now does that mean that all newer engines are tuned to take advantage of greater thermal efficiency to produce better fuel economy while keeping power low? Of course not, but where the 6.0L and 6.4L diesels were concerned I am not sure that they were really any more thermally efficient than older motors. If they were it was just marginally, and Ford felt the need to keep up with horsepower and torque output with GM and the Duramax.

Now this being a Ford site not many will give the Duramax credit for being a revolutionary design in the world of light duty trucks, but it was whether anyone else here will admit it. The Duramax was both more powerful and just as efficient as the competition. Both Ford and Dodge have more or less been playing catch up with this motor since it was introduced. Unfortunately under Ford's previous (incompetent) management the solution was to dump more fuel in the motor and sacrifice fuel economy. This was both cheap and easy, a route that previous Ford management seemed to take every time. Of course International didn't help much either since they seemed disinterested in making anything good or cutting edge.

However this indifferent attitude towards powertrain development was not only in the diesel engine segment or even in trucks. Look at the passenger car engines Ford was turning out from 1999 to 2007 or so. They were all outdated, and generally inferior to their competition in almost every aspect. Thankfully under Mr. Mullaly this is being turned around, he seems to understand that the mechanical bits of a vehicle actually mean something and is giving the engineers at FoMoCo the budget to make some motors worthy of a Ford badge.

So you might wait and see just what a new diesel can do in the fuel economy department while still making ridiculous amounts of peak torque and horsepower.

 

I spent an hour driving one around town today. '11 6.7 CC SB 4X4 XLT.

I averaged around 18 driving around town, WOT was frequent!

I hit the reset button while I was cruising at 72, I think it was around 1600 rpm's. MPG on the display was holding at 16. Flat ground, empty truck, little bit of wind. Not as high as I hoped but it was only for a mile. I was on a two lane 55mph road and I don't like to speed quite that much.

 

Now I'm jealous! I haven't been able to get my hands on one yet...

Do you remember what your brand-new '08 would do under the same circumstances with almost no miles on it? Mine was around 13-14 or so.

If only I could justify such a purchase. Mine just turned 13,000! Have awhile to go...

 

I drove a 11' F-350 DRW Ext. cab 2wd model a while back and that truck was showing 23.2 on the computer read out. That was while driving 55 mph on a by-pass for about 5 miles. I did reset the lie-o-meter when I got on the by-pass. The mileage on the truck was somewhere around 2,000 or 3,000 miles. When I completed my test drive the lie-o-meter was showing 18.6 mpg and that included stop and go traffic with a lot of heavy acceleration.
If these motors hold up durability wise and continue to get good mpg I'll have one in a year.

 

My '08 when new? No I don't remember what it did. I've slept since then.....

My '08 does get around 16-17 hand calc cruising at 2000 rpm's which is about 72 MPH. Drops down 1 to 1.5 mpg's when a regen cycle is happening but then creeps back up after a while.

The '11 I drove around never did a cleanout cycle and I don't have any idea if anything like that even happens with it.

The manual shift mode is the real deal! I like it just as much as I like the new motor!
The display/dash is really good too but I was swerving all over the road going through the different screens. Might as well have been texting or goofing with the iPod. I can see possible lawsuits on this for Ford.

As sophisticated as this thing is, I still don't understand why you cant set the cruise to a specific MPH value!!!! It would be so nice if you could select an exact MPH (like 67) or something rather than play with it trying to be where you want to be.

 

I can see I am just going to have to drive one of these to satisfy my own curiosity!

 

Really? So it's not like the 6.4s?

This is one of the reasons I never liked Caterpillar engines. Setting the cruise at 62 could mean speeds of between 59-64 depending on engine load. You couldn't get full power at 61 unless you manually did it with the throttle.

Does this sound like the 6.7L truck you drove?

And Scott, I'm actually fighting the urge to go and try and test drive one. I have NEVER been able to test drive something I liked without buying it. This is why I purchased 6 brand new cars in the 9 years I've been driving. I'm in the process of buying a house...so I can't test drive one until I close!

 

I know the feeling, besides I just did airbags on mine. Gotta use them some!