E-mail from Cummins on the 04.5 mpg issue

[Big MAK]

Good question on the tow/haul mode. Does tow/haul mode lock out O/D or change all the shift points? If it lowers all the shift points to lesser RPMs I'd leave it in tow/haul and use O/D for coasting on the interstate only. Either way; O/D at 45 is way too slow and low of RPM in town in my opinion -- but then I'm a die-hard manual driver so some of the auto guys need to chime in.



I'll let it coast in the high teens 16-2000 in town but if I need any throttle at all I'm downshifting.

 

[ceastmen]

MVaden



I recieved the exact same e-mail regarding fuel economy in response to my inquiry. i sent them a second e-mail and am awating a response.



I do have to say getting 14. 5 - 15. 0 MPG with a huge heavy truck is still good however it's less than previous generations with comparable HP/Torque ratings which bothers me.

 

[Mopar_Mudder]

Originally posted by ceastmen

MVaden



I do have to say getting 14. 5 - 15. 0 MPG with a huge heavy truck is still good however it's less than previous generations with comparable HP/Torque ratings which bothers me.

What are you comparing it to that would be comparable? The 600 is the biggest ever in a pick-up, just curios what you are thinking.

 

[RobbieH]

MVaden, 2300 miles is NOTHING on these engines. Don't even start worrying until you get 10,000 or even far more miles on it. You haven't even begun to take the assembly lube off yet!



My truck started about 17 mpg, and now gets over 20 mpg on a regular basis if I don't dog the hell out of it. If I keep my foot in it and drive like a maniac I will get from 18. 5 to 19. 5 mpg unladen (every time I hear that word I think of swallows and coconuts). I currently have 17,500 miles on my truck.



Also, as said before, you have to USE IT. I trailer at least 7,000 pounds at least once a month, on fairly long trips.

 

[ceastmen]

Mopar_Mudder,



I was refering to anything produced in the 1980's and early 90's.



RobbieH - Nice Monty Python Reference!

 

[TX Gooseneck]

I just turned 16k miles on my 600. HEAVY towing is and will take up the majority of this cummins life. Case in point, when I left the dealership, I had over 30,000lbs on the truck! My mileage has continued to increase and as I continue to drive it harder and harder, my mileage increases. My cat is now sitting in the garage and I've seen the most dramatic increase in MPG. I'd suggest losing that thing - think of it as a big filter that will get nothing but clogged and kill your mpg and performance.



All in all, I'm happy. I've got one of the heaviest vehicles on the road with a massive frontal area (drw) that has me in the power range of a vette (plus some ). The mileage is decreased from my older cummins, but I've got more weight, more power, more comfort and a much improved vehicle.

 

[rbattelle]

Originally posted by MVaden

Fuel usage estimates are obtained by the U. S. Environmental Protection

Agency during their emissions certification testing. Each vehicle is

tested by professional drivers under precisely controlled laboratory

conditions.

Someone correct me if I'm wrong, but the EPA does not provide fuel mileage estimates on vehicles over 8500 lb GVW. That's why there was no EPA estimated fuel economy on your window sticker (or the stickers of any other HD pickup, or the H2).



Certainly fuel economy and power are directly related (which is why specific fuel consumption, lb/hp-hr, is used to discuss economy). I'd be willing to bet that the SFC for the 600 and the SFC for the '03 trucks comes out to just about equal. But the 600 is making more power, so it's fuel mileage suffers.



Perhaps there are those whose fuel mileage is not what it should be. At the same time, some loss of economy must be tolerated. Look at all those poor souls who bought an H2 and are now inundating GM with complaints that the fuel mileage stinks. It stinks because the vehicle is a beast with a giant gas V8. Since the EPA doesn't require fuel economy estimates, your average H2 buyer doesn't consider fuel economy when buying.



Perhaps it's time for the EPA to begin rating vehicles up to 10000 lb GVW? I'd rather they keep their fingers out of my truck, but at least people would have some idea what they're getting when they buy it!



My lifetime average fuel economy is 18. 5 (46 tankfuls, 20468 mi, 605 hrs, 1110. 5 gallons total burned). That makes my SFC = 0. 043 lb/hp-hr (using a density of 7. 09 lb/gal for Diesel and 305 rated horsepower). Someone with a 600 with similar mileage/hours do this calculation. [Note: the saavy mathmaticians will note that the use of the rated horsepower rather than the average horsepower will WAY underestimate the actual mean SFC. But if everyone follows the same method, the results can be compared in a meaningful way!]

 

[rbattelle]

Originally posted by RobbieH

(every time I hear that word I think of swallows and coconuts).

Hee hee! Me too!:-laf

 

[klenger]

If you can afford to buy an H2, you can afford to buy the gas. Some people!!

 

[mklucas]

The current average on the latest 600 MPG poll in the other 3rd gen. forum is 15. 85MPG. 18-19MPG seems to be the average MPG for the 555. Considering that all of those 600's are brand new, the MPG of the 600 doesn't appear to be too far off - they also have a bit more power.



Personally I don't see what the big deal is.

 

[OHale]

The current average on the latest 600 MPG poll in the other 3rd gen. forum is 15. 85MPG. 18-19MPG seems to be the average MPG for the 555. Considering that all of those 600's are brand new, the MPG of the 600 doesn't appear to be too far off - they also have a bit more power.



Personally I don't see what the big deal is.

Bingo.

 

[MVaden]

This is to Doldenberg, MiKelley, NSperduto and everyone else that read my previous post on my brothers 6. 0 powerstroke milage.



I called little brother to verify his milage and make sure I didn't misunderstand him, and I did not.



He did tell me that, and I believed him, problem is, he was yankin my chain. His words were "Aww heck, I was just tryin to make you feel bad for buying a dammed ole' Dodge".



I sure love my little brother, but..... well anyway, he is not getting 19 mpg. He said on his last tank he got 15. 2 which was on the hwy unloaded on his way to Mississippi to pick up a new puppy. (Black lab) He said he ran between 75 80 mph.



Sorry for the inaccurate info.

 

[JWerkheiser]

My first three fillups:



12. 01 MPG

12. 78 MPG

12. 02 MPG



All were easy on the pedal and half highway/half city miles. Never faster than 60 mph. Scared to think what it would be if I was hammering it.

 

[Floor It]

If you put a pressure box on your MPG could be worse due to the extra fueling on the last pilot injection. I wont mention who but he's working on trying to delete the last injection cycle.



John

 

[MikeKelley]

Originally posted by MVaden

This is to Doldenberg, MiKelley, NSperduto and everyone else that read my previous post on my brothers 6. 0 powerstroke milage.



I called little brother to verify his milage and make sure I didn't misunderstand him, and I did not.



He did tell me that, and I believed him, problem is, he was yankin my chain. His words were "Aww heck, I was just tryin to make you feel bad for buying a dammed ole' Dodge".



I sure love my little brother, but..... well anyway, he is not getting 19 mpg. He said on his last tank he got 15. 2 which was on the hwy unloaded on his way to Mississippi to pick up a new puppy. (Black lab) He said he ran between 75 80 mph.



Sorry for the inaccurate info.

I knew it couldn't be true, but I thought we would never here from you again. I never expected you to post a retraction. You are alright man!

MK

 

[rbattelle]

Originally posted by JWerkheiser

My first three fillups:



12. 01 MPG

12. 78 MPG

12. 02 MPG



All were easy on the pedal and half highway/half city miles. Never faster than 60 mph. Scared to think what it would be if I was hammering it.

When you fill up, how careful are you to get the tank completely full?

 

[JWerkheiser]

I always fill it to the same level at the same station, same pump just to make it as accurate as possible. Going on a 400 mile trip today. Will see how it does.

 

[MVaden]

PKitchen, I sent your questions to The Powermaster @ Cummins, I will post as soon as I hear back.



Now, as far as the poor mpg with my truck, I think I'm going to do just what Big MAK and some of the other guys inluding the PowerMaster @ Cummins suggested, and that is to work it hard and quit babying it.



I'm getting tired of worrying about the milage right now. I just want to enjoy the truck and use it for what I bought it for.



After a few thousand more miles I will figure my milage and if there is no improvement then I will pursue DC for a fix.

 

[geusterman]

TX Gooseneck... thanks for jumping in with the dead kitty. Do you have some data for us... real numbers? I know it is a hassle to fill it all the up a couple of times but we all would appreciate it. Any distinct differences with the dead thing would be appreciated as well. George

 

[Boondocker]

MPGs

I'm going to weigh in on this subject even though I don't have a brand new 2004. 5.

I bought my truck brand new in Dec of 2001, last of the 2nd Gen. The first thing I did was drive it from Oregon to Las Vegas, and frankly, I was a little dissappointed at averaging only about 16 MPG. I picked up about 1 MPG per 10,000 miles for the first 30,000 miles. The engine mods, EZ, RV275 injectors and TAG netted about 1 MPG improvement. Adding a tonneau cover gave me yet another 1 MPG (freeway driving). My last 3 tank fulls, since the addition of the tonneau, typical commuting, mostly freeway averaged 20. 5 MPG! The truck is a 4x4 and weighs 7200 lbs. with me, a very heavy 5th wheel hitch and a full tank of fuel.



I drive pretty conservatively for the most part, but rarely a trip goes by when I don't hammer it at least once . When towing my 10,000 lb 5th wheel, I get in the mid 12s. I'd like to improve the towing MPGs, but the weight and aerodynamics make that difficult.



The morals of the story here are:

BREAK IT IN - anywhere from 10K to 30K depending on load

Tweak the aerodynamics if possible, running over 65 mph, forget it.

Maybe some future engine mods will help



Enjoy your truck!

Neil