Dodge Cummins Diesel Forum banner

1 - 20 of 46 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter #1
I have a 2007 2500 5.9L extended cab, long bed, with 3.73 positraction rear end, automatic transmission and no modifications of any kind. The mileage is currently about 68K miles. I used to get 22-23mpg average (I normally drive 55-65mph on the highway). Since about 50K miles I have lost fuel economy and am only able to get about 20mpg. I have tried a K&N air filter - no improvement, went back to Mopar air filter. I have had the fuel filter replaced at the dealership, no improvement. I have also run several bottles of Lucas fuel treatment through the fuel system, no improvement.

Both batteries have been replaced and the cables and posts were cleaned. This corrected a misfire upon starting. The computer has been reset several times with my code reader with no improvement. I am taking the mpg average from the overhead console. The truck has only occasionally been used for towing a 24ft. travel trailer. The mpg average always dropped some from towing, but would always come back to the 22-23mpg average after some additional driving.

Oil and filter changes have been regular and done using Mopar filters. I did the oil changes myself and have seen no issues related to filter changes.

Ideas?

Joe
 

·
TECH SPECIALIST
Joined
·
11,161 Posts
welcome to cummins forum Joe...

2 things...

one, go here Newbies guide to your new to you truck and consider using the ATF/2SO mix to clean the fuel system. if your injectors are clogging up at the tips, the spray pattern and amount will go down which will change the ignition delay in the cylinder which will change performance and mpg. With you towing its probably not an issue, most of the time its on daily driver trucks that rarely see a load like mine which is next to never. Do some research on the additives and make the right choice for you & your truck. Lots of debating on it.

two, consider using a stiction eliminator in the oil. Once upon a time my higher mileage motor (at the time, 380k (?)) was consuming 3~4 qts of oil in about 7k miles. tried the stiction eliminator and that consumption went down to approx 1 qt in 10k miles (my OCI). I suspect the rings were sticking allowing the oil loss.
 

·
Registered
Joined
·
998 Posts
The overhead should never be used to gauge mpg. Not ever. Need to get some hand calculated tanks and see where you are. They can often read 4-6mpg high if not more.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #6
The overhead should never be used to gauge mpg. Not ever. Need to get some hand calculated tanks and see where you are. They can often read 4-6mpg high if not more.
I have consistently used the overhead console to check fuel economy. I have made occasional checks using the odometer and recording fuel used which confirms what the overhead console is reporting within about .2 to .3 mpg. I understand that trip computers etc. can be an issue, but I just have not seen it on this truck.

One thing I did when we built our current home in 2004 was that I had an extra long attached garage built that would hold the truck with room left over. So this truck has been indoors all these years except when I drive it. Before this truck I had a 1995 Dodge with the 6BT engine, 3.5 rear end and automatic transmission. It got slightly better fuel economy but was lacking in power. This current truck has been great in all respects except the loss of fuel economy in the last 1.5 years or so.

Joe
 

·
Registered
Joined
·
16 Posts
Discussion Starter #7
One thing I should mention is that when the OEM batteries began to fail, it caused a loss of fuel economy. When I replaced the batteries, the fuel economy returned to normal. I have not taken the truck in to my dealer for diagnosis on this issue, so perhaps I should do that and see what they estimate or determine the problem is.
welcome to cummins forum Joe...

2 things...

one, go here Newbies guide to your new to you truck and consider using the ATF/2SO mix to clean the fuel system. if your injectors are clogging up at the tips, the spray pattern and amount will go down which will change the ignition delay in the cylinder which will change performance and mpg. With you towing its probably not an issue, most of the time its on daily driver trucks that rarely see a load like mine which is next to never. Do some research on the additives and make the right choice for you & your truck. Lots of debating on it.

two, consider using a stiction eliminator in the oil. Once upon a time my higher mileage motor (at the time, 380k (?)) was consuming 3~4 qts of oil in about 7k miles. tried the stiction eliminator and that consumption went down to approx 1 qt in 10k miles (my OCI). I suspect the rings were sticking allowing the oil loss.
Steve;

Thanks for the suggestion. I will try the ATF/2SO mix to clean the fuel system and check the reccomendations on the link you provided.

Joe
 

·
TECH SPECIALIST
Joined
·
11,161 Posts
One thing I should mention is that when the OEM batteries began to fail, it caused a loss of fuel economy. When I replaced the batteries, the fuel economy returned to normal. I have not taken the truck in to my dealer for diagnosis on this issue, so perhaps I should do that and see what they estimate or determine the problem is.

Steve;

Thanks for the suggestion. I will try the ATF/2SO mix to clean the fuel system and check the reccomendations on the link you provided.

Joe
Make sure you get the dex/merc ATF, it is a non-synthetic and TW-C3 2 Stroke oil... 8-12 oz of ATF & 24-32 oz of the 2SO. Another thing that can affect mpg is the trans/torque convertor... When I swapped mine from an AT to MT the guy I sold my mildly built trans & TC to was consistently getting 12 mpg since new. He hand calculated the mpg on the way to the shop ~200 mi, and then on the way back after the install. He called me the next day and he told me he managed 18 on the way back. Asked him to stay in touch & let me know how it goes moving forward. He got back to me a couple of weeks later and said he was in the 17's consistently. Just from the trans swap. So whatever the issue was with his original trans, it did not exist in mine. His truck was a MC 4wd, lifted with big tires.

take it fwiw...

Also, If you already have the reverse horn honk ecm download, great. If not... dont go to the dealer otherwise you'll have it and be pissed that it gets installed. Horn honks in reverse with door open & seat belt disconnected.
 

·
Registered
Joined
·
1,410 Posts
Must be a 2wdr and you drive the speed limit with moderate acceleration.

Reaching high mileage area for injectors with only stock OEM POS cheap inadequate fuel filtration. Injectors nozzles already worn out from too much dirt and water=s rust in fuel, nozzles continually leak into chambers during complete 360d rotation. Inj. return valves leak extra return bypass diesel back to tank, throwing off fuel calc. computer. Worst rust out wear of expensive injectors occurs in Cummins that are garage queens and set all the time.

Before new injectors, have to put on commercial HD equipment fuel dirt filter and separate water separator. Cummins, Fleetguard, Donaldson, Baldwin. 3 um max and lots of water holding capacity with easy drain.

ASAP, put a Baldwin PF7977 in the stock OEM fuel filter housing. Only one that comes close to Bosch specs for their fuel system. 5 um.

Want the 4" deep Wix 49946, best dirt filtration for the money. Daimler Mercedes when they owned Dodge, paid WIX to develope this deep fine micron dirt filter with large holding capability and rugged, won't suck in and break from turbo pull.

Mopar filters are a price and quality ripoff. Can find much better filtration, fuel and oil.

Water, rust and dirt in fuel kill these great HPCR Cummins 5.9s
 

·
Registered
Joined
·
16 Posts
Discussion Starter #10
Make sure you get the dex/merc ATF, it is a non-synthetic and TW-C3 2 Stroke oil... 8-12 oz of ATF & 24-32 oz of the 2SO. Another thing that can affect mpg is the trans/torque convertor... When I swapped mine from an AT to MT the guy I sold my mildly built trans & TC to was consistently getting 12 mpg since new. He hand calculated the mpg on the way to the shop ~200 mi, and then on the way back after the install. He called me the next day and he told me he managed 18 on the way back. Asked him to stay in touch & let me know how it goes moving forward. He got back to me a couple of weeks later and said he was in the 17's consistently. Just from the trans swap. So whatever the issue was with his original trans, it did not exist in mine. His truck was a MC 4wd, lifted with big tires.

take it fwiw...

Also, If you already have the reverse horn honk ecm download, great. If not... dont go to the dealer otherwise you'll have it and be pissed that it gets installed. Horn honks in reverse with door open & seat belt disconnected.
Yes, my truck already has that annoying feature.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #11
Must be a 2wdr and you drive the speed limit with moderate acceleration.

Reaching high mileage area for injectors with only stock OEM POS cheap inadequate fuel filtration. Injectors nozzles already worn out from too much dirt and water=s rust in fuel, nozzles continually leak into chambers during complete 360d rotation. Inj. return valves leak extra return bypass diesel back to tank, throwing off fuel calc. computer. Worst rust out wear of expensive injectors occurs in Cummins that are garage queens and set all the time.

Before new injectors, have to put on commercial HD equipment fuel dirt filter and separate water separator. Cummins, Fleetguard, Donaldson, Baldwin. 3 um max and lots of water holding capacity with easy drain.

ASAP, put a Baldwin PF7977 in the stock OEM fuel filter housing. Only one that comes close to Bosch specs for their fuel system. 5 um.

Want the 4" deep Wix 49946, best dirt filtration for the money. Daimler Mercedes when they owned Dodge, paid WIX to develope this deep fine micron dirt filter with large holding capability and rugged, won't suck in and break from turbo pull.

Mopar filters are a price and quality ripoff. Can find much better filtration, fuel and oil.

Water, rust and dirt in fuel kill these great HPCR Cummins 5.9s
Yes, it is a 2WD model and I do drive the speed limit and avoid excessive acceleration. Of course there are times that require fast acceleration, particularly on-ramps to interstate highways etc. Most of my driving ranges from 55-65mph. I live in the country so all trips I make are 25miles one way or more. The truck gets fully warmed up.

One thing that did happen before I discovered it was that a fuel station I used changed to adding bio-diesel to the fuel. I did not realize the change had been made until I had refilled a number of times. I changed to a different fuel station which does not have bio-diesel added.

I guess my truck qualifies as a garage queen, since it only has about 68K miles in spite of its age. I am retired and don't drive as much as I used to.

When I had my '95 model I used to take it to Cummins Southern Plains service in the Dallas area. I always had them do the valve adjustments. I see that for the 2007 5.9L I have the factory only recommends valve adjustment at either 135K miles or 150K miles. I am wondering if I would be better off going there to have the injectors checked instead of the dealer where I bought the truck (Sherman, TX). It is over an hour drive to the Cummins location, but I will gladly do it if they can do a better job of diagnosing the cause of the poor fuel economy.

Joe
 

·
Registered
Joined
·
10,348 Posts
The Chevron's here in San Diego have stickers now stating contains 5-20% biodiesel. Another independent station in Leucadia north of here has a sticker stating 20% biodiesel. I'm avoiding them. I have the Baldwin canister filter,a GDP cylinder head 3 micron and a frame mounted water separator filter. The stock and GDP was probably plenty. My friend has maintained a fleet of drill rigs and some Duramax LT's for ages and has never found water in the fuel. Lucky I guess.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #13
Yes, Chevron is affiliated with Exxon-Mobil back through the Standard Oil Co. of the Rockefeller origin. I first quit using Walmart diesel then Exxon after each changed to bio-diesel. Unfortunately in both cases it was a while before I noticed the pasted label on the pumps saying it contained bio-diesel. I suspect this may be the cause of the issue I am having. The truck began to emit lots of black smoke (a huge cloud of it) when I accelerated hard in on-ramps. I have seen other Dodge Cummins trucks of the same period do the same thing. The exhaust pipe became quite black inside. Now that the truck has been fuled with pure diesel since then the black smoke has pretty much disappeared. I need to try the oil and fuel filter plus the flush-out method mentioned earlier in this thread. Those are not too expensive and if they produce an improvement that is great. If the issue continues unabated then I will go to either the dealer or Cummins to see what the real source of the problem is. I am leaning toward going to Cummins as they are the experts on this engine.

Since I am retired I have to watch my expenses and if the solution to the fuel economy turns out to be thousands of dollars, I may just have to sell the truck and go back to a late model used pickup with a gasoline engine. I have been mostly a Mopar guy over the years, but I have also had AMC, Ford and lately Hundai and Subaru. Dodge has been having camshaft and valve lifter issues on their 5.7L hemi engines and I don't want to buy something that is going to have troubles that involve having to dig into the engine to correct. I am now 77 years old and physically no longer able to do many of the maintenance items myself like I used to. I have continued to do oil & filter changes, air filter changes, cleaning of battery cables periodically etc. The coolant has been replaced at the dealership.

Are we saying that the Mopar fuel and oil filters were inadequate to begin with or that they became inadequate due to changes in the fuel formulations available at fuel stations? I understand going to smaller micron filters as I had to also do that with the water filters on my well pump here at home.

Thanks for all your help guys!

Joe
 

·
TECH SPECIALIST
Joined
·
11,161 Posts
just do the mix in the fuel and switch the fuel filter over to the pf7977. Drive if with the mix and check it afterwards. 68k(?) is nothing on thes motors and the injectors have lots of life left.

if your mpg went from 22 down to 16-17 yeah you probably have a problem. hand calculate the mpg on the truck as is, then run the mix and report back after the following tank. changes in fuel can change mpg like the bio mentioned.

in my opinion, there is nothing wrong with your truck based on the discussion. any trip to the dealer for this would be wasted $.
 

·
Registered
Joined
·
10,348 Posts
I ran a few tanks of Propel HPR through the truck due to some gift cards I received and from friends. I did see a reduction in fuel economy with that fuel andt I couldn't make the truck smoke and the exhaust smell is almost non-existent. I haven't used any since and it's been yrs now as I was concerned about the scouring action. I hope Newsome and CARB doesn't force 20% bio down out throats to appease the touchy- feeley hoards that dominate this once great state. CARB tried to increase the ethanol blend to 20% until the manufacturers informed them of the damage to older vehicles. The friend of the working man in action again.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #16
Steve and Danderson;

One positive thing I can report is that after running three Lucas injector cleaner bottles through the truck, the excessive smoke in the exhaust went away, so it did apparently help somehow. I will do the cleaning suggested and then report back. I will check to see if the needed items are available locally. If not I can order them on-line

A friend said that at 68K miles the truck is not broken in yet. The same was true with my '95 model. I bought that one when I was still working. I even added an air-bag suspension to the rear axle so I could raise and lower the 5th wheel hitch and level the camper after hitching up. It was nice to have, but when I bought the current truck The cost had gotten too high and it turned out the suspension on this HD 2500 was just right for the Carrylite 32ft fifth wheel. Since then we sold that camper and no longer do the camping. Our daughter uses the truck occasionally now for her 24ft. travel trailer. The truck hardly knows that camper is behind it. I mostly use the truck now for lumber or other supplies from various locations back to the house.

Thanks once again to all of you!

Joe
 

·
Registered
Joined
·
10,348 Posts
Another thing I do is after thoroughly warmed up I make a half dozen full throttle runs for a short distance. I drive for fuel economy and the cat can soot up. A retired Mopar Ram tech advised me of this. Trucks would come in with the complaint.
 

·
Registered
Joined
·
11 Posts
Make sure you get the dex/merc ATF, it is a non-synthetic and TW-C3 2 Stroke oil... 8-12 oz of ATF & 24-32 oz of the 2SO. Another thing that can affect mpg is the trans/torque convertor... When I swapped mine from an AT to MT the guy I sold my mildly built trans & TC to was consistently getting 12 mpg since new. He hand calculated the mpg on the way to the shop ~200 mi, and then on the way back after the install. He called me the next day and he told me he managed 18 on the way back. Asked him to stay in touch & let me know how it goes moving forward. He got back to me a couple of weeks later and said he was in the 17's consistently. Just from the trans swap. So whatever the issue was with his original trans, it did not exist in mine. His truck was a MC 4wd, lifted with big tires.

take it fwiw...

Also, If you already have the reverse horn honk ecm download, great. If not... dont go to the dealer otherwise you'll have it and be pissed that it gets installed. Horn honks in reverse with door open & seat belt disconnected.
Quite possibly the most annoying thing I've ever encountered... The reverse horn honk.
 

·
TECH SPECIALIST
Joined
·
11,161 Posts
Quite possibly the most annoying thing I've ever encountered... The reverse horn honk.
The easiest fix is to ditch the AT and go to MT (y)
 

·
Registered
Joined
·
11 Posts
hello, so I have a 04.5, 233k miles. 2 months ago my mileage dropped from 23-24 to 16-17 highway. ( hand calculated) original owner......replaced injectors because it was time, no change. Sent turbo(35k miles on it) back to shop for checks,, everything fine. Replaced MAP and FCA,,,, no changes.....fuel filters, air and oil changes done. Ot seems no one can fix when this goes wrong. Some people don't believe trucks can get good fuel mileage. However I have 233k miles and 16 years with a truck that did, no it has stopped. So I feel your pain.
 
1 - 20 of 46 Posts
Top