Fuel Milage Issues

[dakingsella]

I have a 2011 Ram 2500 (first Diesel ever) that I purchased new. Since the begining I have experienced some strange fuel efficiency issues. At times I get 17 MPG on the highway at other time I get about 12 MPG under the same or similar conditions.



I can tell when the fuel efficiency is good and when it is crappy by watching the instant milage indicator. When I am going downhill it will peg to the right when it is running good, but won't go above 20 MPG when running crappy. It is not posting any codes and doesn't feel any different than when it is running good.



It seems that sometimes I can pull over, turn the ignition off and restart and it will run better but other times that doesn't help. It remindes me of the symptons that would indicate a stuck choke on an old carburetor gas engine.



I have about 16000 miles on the truck, have performed all recommended service and have had it into the dealer specifically to have the fuel milage issue addressed. They didn't find any codes, but did upgrade the engine software which interestingly added about 1 MPG to both the crappy and good Avg. MPG.



I have validated the accuracy of the Avg. MPG readings by manually calculating the MPG at fill-up. It is spot on (within . 1 MPG Average).



What is really frustrating is their attitude that they can't do anything to find the problem unless there is an engine code posted. I have called other dealers in my area and get the same answer "We can't do anything unless there is an error code".

 

[crabjoe]

There's no problem. . It's doing what it's supposed to to... When your MPG drops, you're experiencing DPF regeneration.

When DPF regeneration occurs, your engine will dump extra fuel into your exhaust to burn out the soot in the DPF. That's why you see a MPG drop.

 

[dakingsella]

I thought I would get a EVIC Message when regeneration occured. If regenerating is the cause then it is regenerating more often than not. How often should regeneration occur?

 

[AH64ID]

Just as Joe said its your regenerations.

The EVIC will only show you regeneration when your above 80% full.

I have heard that every 150-180 miles is average on a '10-'12.

 

[RUSSELL5000]

dakingsella:



Regenerations occur with varying degrees of frequency based on engine load. You normally should not get any message on the EVIC. There are a bunch of past articles in the TDR -start looking at past issue article indexes. There is also a good introduction in the Buyer's Guide. The most recent issue has a cool little article at the end by Kevin Cameron - nice little summary. There is a ton of information in these articles on how this "wonderful" system works.



I am newby this year, but one thing becomes clear pretty quick: emssions requirements are a big driver in how these trucks work. So, it will be worthwhile reading.



As a plus you'll get to learn around 500 new acronyms (ok, small exaggeration - but there are a bunch).

 

[Powder Extreme]

That does seem excessive, usually regeneration will only drop a couple mpg. There has been reflashes that address regeneration issues, wouldn't hurt to make sure you have the latest software.

 

[dakingsella]

The latest engine software update was applied about a week ago. It seems to have improved MPG slightly. It seems like my MPG is reduced more than what I expect. Is any regeneration data available as an ODB output?

 

[AH64ID]

The one friend of mine that watched his very close, pre-deletes, would go from 18-20 to 12-13 during a regen on the instant readout.

 

[Powder Extreme]

The latest engine software update was applied about a week ago. It seems to have improved MPG slightly. It seems like my MPG is reduced more than what I expect. Is any regeneration data available as an ODB output?

Yes there are a few gauge displays as well as tuners that will display when the motor is in regen mode, chec out the electronics forum. Edge products is one that comes to mind.

 

[Jim W]

A simple gage will tell you exactly when you are in regeneration mode of your DPF an EGT gage. I installed an EGT gage and when I was stock I would see a change in EGT temps. They would rise from 800F to as much as 1450F, the EGT's would stay between 1100 and 1250F for 20 min's or so climbing as high as 1450F and then returning to the 1100 or 1250F range. The rise in the EGT temps would also coincide with a decrease in fuel mileage reading on the EVIC. When the temps would start to rise I would clear the MPG reading and would see the new readings on the EVIC and this could be as low as 6 or 7 MPG's when towing and in regen mode.

I also tended to regen about every 200 miles or so when towing for long distances.

Jim W.

 

[gtoli]

An Edge Insight will show when the truck is in regen, as well as many other parameters.

 

[RUSSELL5000]

dakingsella:



I looked at my stack of paper last night.



Page 126 of TDR Issue 81 is a good oversight of the emissions system.



Page 32 of TDR Issue 72 and page 42 of TDR Issue 74 contain real life analyses of regeneration and its cost. I think those articles are exactly what you are looking for.



The EDGE Insight CTS plugs into the ODBII port and monitors a bunch of stuff, one of which is regenration status. That is how the regenerations were tracked in the TDR articles above. If you have not already been to the Geno's Garage website I suggest stopping in. Good reading there (I hide my wallet before I look, however).





I am still learning, but there is something else to consider on the 07. 5 through 12 trucks: frequency of oil changes. Lots of exhaust gas is pumped back into the cylinder to keep combustion temperatures down so less NOx is produced. Lower combustion temperatures mean more soot. So lots of exhaust with soot is pumped into the cylinder and lots of soot is made. That littlte bit of exhaust gas that gets by the rings and little bit of oil not perfectly wiped allows a lot of soot to get into the oil. The DPF is exactly what is says it is: a filter. If it does its job of filtering out soot then it gets full of soot. We get rid of the soot by burning it into ash. We dump fuel into the cylinder during the exhaust stroke so the exhaust gas will burn nice and hot and heat up the DPF, burning the fuel to ash. Some of the fuel slips buy the rings, diluting the engine oil. The point of this story is that we have to change the oil and filter more often in the 07. 5 through 12 trucks than was true for earlier trucks.



The 13 and subsequent trucks scrub out NOx using the mopre effective DEF/SCR approach. Better scrubbing of NOx means higher combustion temperatures can be allowed. Less exhaust gas is pumped back into the cylinders and less soot is produced. Since less soot is produced the DPF easy bake oven is not fired up as often. Less soot in the exhaust and less fuel dumped into the exhaust for regeneration means cleaner oil and better fuel mileage.



Those who are a lot more knowledgeable than I can correct all my mistakes in the above.



I have 10,000 miles on my 2012 2500 4WD. I averaged roughly 18 mpg unloaded on the interstate at the speed limit. I averaged roughly 11. 5 mpg pulling my 9K travel trailer with truck loaded with gear and people. My regeneration experience is very much like the articles describe and as others have said.

 

[dakingsella]

Russell

Thanks for the information and references. Your explaination makes a lot os sense. I am on the road right now. I pull an 11K 5th Wheel with the truck and my milage while pulling has always been satisfactory, I get almost 13 pulling. But don't get much better empty.

I'll do the research based on the references you gave me when I get home next week. Where I am staying I have very limited internet access.

 

[wyosteve]

I don't disagree with what Russell said in general, but the more frequent oil changes only occur if the truck is not used in a fashion to burn off some of the excess fuel, warm up, etc. In fact, on my 2012 the oil changes have been less frequent than on my 04. 5. On the 04. 5 I was changing oil every 5k miles. If I wait for the 'oil change due' warning on the 2012, it's been 6000 to 7000 miles between changes. Of course I tow something regularly and don't make a lot of short stop and go trips. Just my . 02.

 

[crabjoe]

I don't disagree with what Russell said in general, but the more frequent oil changes only occur if the truck is not used in a fashion to burn off some of the excess fuel, warm up, etc. In fact, on my 2012 the oil changes have been less frequent than on my 04. 5. On the 04. 5 I was changing oil every 5k miles. If I wait for the 'oil change due' warning on the 2012, it's been 6000 to 7000 miles between changes. Of course I tow something regularly and don't make a lot of short stop and go trips. Just my . 02.

How are you determining oil change frequency? When I had my '04, I had the oil analyzed, and even with 10K miles on dino oil, it would come back as good to go...

BTW, if I had a non SCR Ram with DPF, I'd be getting the oil analyzed. I've seen to many posts where the oil has been diluted from regens, to trust the EVIC.

 

[AH64ID]

The EVIC is actually pretty accurate on the trucks with the current flash, it comes on at the proper time for 5% fuel dilution or miles. The few tests I have seen show the real fuel dilution right under 5% when the light comes on. I would trust it, and change it accordingly.

 

[RUSSELL5000]

dakingsella:



Which oil and oil filters to use are addressed thoroughly in TDR articles by John Martin - I used these articles to decide on which oil and oil filters to use. As the TDR notes, oil preferences are as passionately held as political and religious preferences. I have also concluded that the only way to really know when oil should be changed is by an analysis. There are really good articles on this in the buyer's guide as well as the magazine. I found them very useful because I did not have any strongely held beliefs - I guess you would say I was an oil agnostic.



So, I'll offer my opinion and make no effort to claim it is correct nor defend it if someone says it is incorrect. I use Shell Rotella oil and the FleetGuard Stratapore oil filter. I made these choices after careful reading of the TDR articles. I get the oil at WalMart, the filter at Geno's Garage.



I believe the 2007. 5 through 2012 model years carry more soot suspended in the oil and are exposed to more fuel dilution than earlier model years and 2013 and subsequent model years. An oil change costs $55; an oil analysis would cot $30. I expect I will change oil every 3,000 miles because of the soot loading and fuel dilution and also despite the fact the maintenance schedule says 7,500 miles. So, if I round up, I'll change oil 34 times in 100,000 miles rather than 14 times in 100,000 miles according to the maintenance schedule. In terms of dollars, I'll spend $1,870 versus $770, or $1,100 more. It will probably take me ten years to put 100,000 miles on my truck, so I figure an extra $110 per year. I also change all other fluids and filters more often than the maintenance schedule requires. If I had a 2013 model year I would probably change every 5,000 or 6,000 miles - still much more frequently than the 15,000 mile maintenance schedule. I'd rather spend money on filters and fluids than suffer problems.



This is incorrect according to the articles in the TDR and I am certain an oil analysis would show not required. Same holds true for all other fluid and filters. On the other hand, this truck is by far the most expensive vehicle I have ever purchased, and I don't mind spending a couple hundred dollars per year more than may be required to keep everything safe. Purely a matter of personal perspective and comfort.



The TDR and this forum are outstanding resources to learn anything you want to know about your truck and decide how you want to do things.

 

[WStephens]

I change my oil when the CVIC tells me to or if I know I am making a long trip and there is a possibility that it may go off while on the trip. I run a spread sheet for my fuel mileage and in the notes I type in when I change the engine and drive train oil so I have a reference and the average is about 5K between the oil changes. It depends on how hard I work the truck how long the drain interval is the harder I work it or drive long distances the longer the drain interval if I go into town I drive like I stole it. I also use Amsoil oil and filters in the truck unless Amsoil does not have a recommended oil or filter. So for not I am using the new Fleetguard Nano Net fuel filter but the engine, transmission, transfercase and axles all have Amsoil lubricants in them.



My 2005 I went by the light duty schedule to change the oil and would still have it but when the injector lines were changed and the nozzles changed on the injectors it had a no start that could not be explained. The Dealer and I did not trust it and the new 5th wheel was to heave for a 2500.