Fuel Economy

[Vaughn MacKenzie]

Hi all, I am shopping for a late model 3rd Gen to replace my aging 2nd Gen. I am concerned about fuel economy with the 6.7 though. It will be a daily driver so this matters. What are you all seeing in general, with the 6-speed auto? Please indicate if you have any tuner/deletes or stock.

I am also looking for a 2006/7 5.9 with manual trans, but those are hard to find.

Thanks all!

 

[Jim W]

I have an 2008, 2500 Ram Mega Cab with the 68RFE auto and the 6.7L Cummins. I am using a Smarty S67 which adds 60HP/120 lb.-ft. of TQ to the engine.
When I was stock I would see on a regular bases in city /rural driving after the first 10,000 miles between 11 and 13 MPG. I did tow a 5er also at that time a smaller unit then I have now, but the mileage was also as low as 9MPG's.

After 21,000 miles when the Smarty was installed my city/rural mileage is between 14 and 16 MPG with a high of 18 MPG (all highway driving). Towing mileage varies by wind condition and terrain, but usually around 11 MPG's. I might be able to see a little better fuel mileage in city/rural driving but I like the get up and go of the truck to much.

I have 12 years of data recorded on my spread sheet for my truck.

 

[Bob4x4]

The worry with a 3rd gen 6.7 should be based on emission failures not fuel mileage imho

 

[BrianAtSmarty]

Good morning Vaughn,

Dont do it Vaughn! Avoid the 6.7 garbage. My 07.5 2WD SRW Regular cab is an 11 mpg truck empty on the open roads often dropping to 9 mpg. One cannot drive in the city as it needs frequent re-gens. One cannot drive in the snow as to be safe you must go slower and clog up. Fog? forget it. Park it and drive something else. The DPF plugs frequently so I find myself sitting at stoplights with the trans in Neutral and the foot to the floor running it against the governor all the time it is sitting. It still has issues even with the Smarty installed or uninstalled. It has left me stranded multiple times. And when it finally does go into regen you can view the fuel gauge move. I am going back to a 12 valve Vaughn. I want dependable again. Also simplicity and I want to stop paying for expensive repairs on emissions. These 6.7's are no longer a million mile engine like the 5.9 was. Then add 15K for emissions and $4,000 for CR injector changes... 4K to replace the clogging VGT turbo. These newer 6.7 trucks are no where as dependable nor do they have the longevity of the older Cummins. I cannot delete. I've had to carry a brick to place on the go-pedal. Stick the truck in neutral, set the park brake, stick a brick on the pedal and walk away and enjoy lunch for 45 minutes while your truck sits at 3500 rpm as you hope that will help clean the DPF.

You won't like it Vaughn. Keep the VP truck................

 

[xcc_rider]

I see your login still works.

Brian and Bob are right, the emissions on these things make them unreliable and a pita.
I also have first hand knowledge of this too.

In the past I ran emissions legal SmartyJr 60hp tuning with the egr valve actuator unplugged and liked it better than stock.
Reduced regen durations and frequency and increased reliability due to removing a key problem component from the system.
Regens were still a pain but enjoyed the tuning all the same.

Current configuration:
2007.5 2wd mega 68rfe 373's deleted w/SmartyJr on stock power.

highway - 18-21 mpg empty
towing - 10.5-11.7 mpg w/9k 5th wheel
city - who knows? Most everything around me is 50 mph+

If you can delete then a 6.7 is very reliable.
If not then go with a 5.9.

 

[cerberusiam]

Same thing from my experience, emissions intact and efficiency is counter productive. The engines are much more efficient once all that problematic stuff is removed. Unfortunately, once you do that the HG becomes a failure point. The 68RFE is a good unit once all the cheap OR parts are replaced and the tuning done correctly, just like the engine you have to run them pretty much bone stock or drop the $$ to fix them right.

 

[Vaughn MacKenzie]

Thank you all for the input. I had heard before mileage on deleted rigs can be around 20-21 on the highway, but I am a little skeptical of that.

My '98 2wd short box auto gets 19.5-21 highway, at 70-73mph. Towing my 24' Argosy (1970s Airstream) I get 14-15.5 even with the lousy gearing, winding it up in Drive or lugging it in OD. I may stick with what I have for a while longer but I have been having a lot of age related issues. It's my primary daily driver so at some point I need to get a newer truck.

 

[Cummins12V98]

Fix it as ya go!

 

[steeve]

My fuel economy (according to the overhead display) fluctuates greatly from 15 mpg at beginning of a trip to as high as 24 MPG at the end, over about 100 mile distance, then does the same thing on the return. this has happened all 4 trips. I am new to owning Dodges and to Diesels. I wish I had known about the programming and emissions issues with the 6.7, before I bought my used 2008 model recently. I should have got an earlier model with the 5.9 engine which is supposed to get better fuel economy.

 

[SteveHH]

Looking for info on tuners, delete, etc. and found this. I lost about 4 - 5 mpg going from my '03 5.9 M6 to my '17 6.7 68RFE. My DD so am interested in MPG gains too. Is there a web site comparing potential gains with various tuners as well as how they work with deletes?

 

[tommyturbo]

Hi all, I am shopping for a late model 3rd Gen to replace my aging 2nd Gen. I am concerned about fuel economy with the 6.7 though. It will be a daily driver so this matters. What are you all seeing in general, with the 6-speed auto? Please indicate if you have any tuner/deletes or stock.

I am also looking for a 2006/7 5.9 with manual trans, but those are hard to find.

Thanks all!

SteveHH. You didn't mention any towing use, but if you do then the 6.7 is a better choice because of
the EB and 6 speed auto. The smog stuff is the famous problem child. I have no choice but to
keep emissions intact in CA but if the system is understood and maintained then the CTD runs
super and doesn't disappoint. Mine also is a daily driver and does not even warm up commuting
and tows hard three or four times a year. The only time I had trouble with the smog stuff was the EGR.
When it started sticking, all kinds of codes popped up, turbo acted up, limp modes, ect. Cleaning didn't
help so I replaced it with a latest OE part number. Everything went back to normal. Other than keeping
the smog stuff hot and happy, there is really no other expenses and worries. The truck is running good
and strong. Mileage was not a factor when buying but but was a lot poorer than expected. It wasn't until
a mild tuner was installed that mpg went up. Using the tow setting, towing torque increased at 1800 rpm
and mpg went up in all driving situations. MPG now is up with the newer DEF fluid CTD's. If you find a CTD
with well maintained emissions, it would be a candidate for a tuner. The Cummins would run more effiently
and get better mpg to boot. Even if you don't have smog testing in your state, I still would recommend keeping
it intact and maintained. Deleting may cause unforeseen problems down the road with expenses. The stock
system still thinks its stock. In CA, my only choice for a tuner was a Banks Automind with C.A.R.B. blessing.
There are others on the market that may do better and have more options but for me, it was the safest and
simplest. I'm only one of many that has such a super running '07 to '12 with emissions intact.
My $.02.
Tommyturbo

 

[SteveHH]

Thanks tommyturbo,
I've had my '17 for a year now and pulled a TT for about 10,000 miles. It seems to take over a dozen miles to warm up completely - the little 10 mile jaunts to the store are where the mpg's suck the worst. I'm thinking of a tuner that will help the mpg's the most yet still work if I do a delete. Not in California anymore so that's not an issue. The mpg's sure suck though, compared to my old '03 5.9 with the manual xmission. I wish I could get it to stay in high gear like if I had a manual - when it downshifts going up a hill it's like a hole opens up in the bottom of the tank. Any tuners adjust the xmission to keep it in high gear?

 

[tommyturbo]

SteveHH. Actually I answered you by mistake. My post was intended for Vaugh Mackenzie and his inquiry into
an '07.5 to '12 non def 6.7. I have no experience with the def group but for you, I know for sure there are good
tuners that can help you with your expectations. Search around the TDR and elsewhere and you will find info whether
you delete or not.
Tommyturbo

 

[tommyturbo]

Thanks tommyturbo,
I've had my '17 for a year now and pulled a TT for about 10,000 miles. It seems to take over a dozen miles to warm up completely - the little 10 mile jaunts to the store are where the mpg's suck the worst. I'm thinking of a tuner that will help the mpg's the most yet still work if I do a delete. Not in California anymore so that's not an issue. The mpg's sure suck though, compared to my old 'builders03 5.9 with the manual xmission. I wish I could get it to stay in high gear like if I had a manual - when it downshifts going up a hill it's like a hole opens up in the bottom of the tank. Any tuners adjust the xmission to keep it in high gear?

SteveHH. Some tuners address the transmission but I don't know if holding on to 6th longer in tow is available. You will have to check that out. Now there are
some on the TDR that have a preferred technique to towing in high gear especially with the 3.42 axle. That is without a tuner. Check that out too.
Tommyturbo

 

[steeve]

I had to quit driving my 08 on less than 30-mile trips, to get the DPF warning to stop and fuel mileage to go back up. I am getting 18 to 24 highway again now, hit 25 once on long trip. average is around 21. It has 176,000 on it now and I expect it will last a good while, as I only am using it once in a while, on just the longer runs. if I wasn't in CA I would delete everything and tune for economy. Wish I knew all this before I bought it. Thank god I don't need to tow anything....truck doesn't even have a hitch. My other car fits in the bed, even clears the fender wells......don't ask.

 

[tommyturbo]

I had to quit driving my 08 on less than 30-mile trips, to get the DPF warning to stop and fuel mileage to go back up. I am getting 18 to 24 highway again now, hit 25 once on long trip. average is around 21. It has 176,000 on it now and I expect it will last a good while, as I only am using it once in a while, on just the longer runs. if I wasn't in CA I would delete everything and tune for economy. Wish I knew all this before I bought it. Thank god I don't need to tow anything....truck doesn't even have a hitch. My other car fits in the bed, even clears the fender wells......don't ask.

steeve. You got the right one. It sounds like its bone stock with emissions functioning o.k. If you are getting the overhead showing 80% full regeneration
required, you are borderline shutting down to limp and see dealer to de-soot. Don't let it go that far. The key to a good running stock truck is to
understand how to keep the DPF happy. You bought the right truck but with a problem child emissions but there is a way to deal with it and
the results will restore your faith in your '08. Let me explain this driving cycle. First you must recognize when the DPF is starting to regenerate.
Without gauges, the obvious sign is the charcoal lighter fluid smell especially in the cab and the muffled sound or quieter exhaust and louder clatter
especially at idle. You need to keep driving over 35 mph for about 20-25 minutes until the exhaust sound is back to normal and clatter at idle reduces and
the charcoal lighter fluid smell isgone, then the most important heavy regen is done. If your driving does not allow enough time to complete this
then plan your next trip to finish this. This should keep the overhead prompt from coming on. The heavy regen consumes a lot of fuel
while processing and hence the black eye for mileage. Things to remember: Turn on the exhaust brake and tow haul full time on start up. This
keeps the turbo vanes freer from soot build up. Exercise the exhaust brake occasionally when traffic permits by throttling up for boost in
3rd gear from 30 mpg to redline and let the exhaust brake bring you back down to 30mph then repeat a few times.
Before shutting down, Let the turbo cool down a least 30 seconds with the exhaust brake off and at least two minutes after exiting a freeway.
Gauges are a nice accessory. I admit that this driving style is really whacked out and I don't expect anyone in their right mind would
follow this but other than doing this, your truck will run beautifully and reliably so you can enjoy your CTD. After you get your truck
running fine, the next step is to address efficiency and mileage. Stock mileage for me was hand calc 17.5 mpg unloaded freeway,
11mpg pulling my trailer and combined city and some freeway was 12mpg and city only was 10.4 mpg.
After installing the Banks Automind, unloaded freeway is 22-23 mpg, combined city and some freeway is 15.5mpg and city only is
12mpg. I'm o.k. with this compared with stock. The Banks is a low cost but a limited canned program tuner but has tire pressure
monitor resetting and tire size for speedo check. The tow tune is my daily tune and puts more torque at 1800 rpm where I
tow at 66 mph in 6th. There is a top tune that I used when not towing which is aggressive and right foot savvy is needed to keep the
68RFE from shredding. The tow tune is safe. There are other tuners out there but I don't know if they are C.A.R.B. legal.
If you want to try this and have questions you can PM me for details.
Tommyturbo

 

[steeve]

Thanks for the details. I have not had the DPF warning (80%) display, since I drove to Colorado in June hauling my other car in the bed. I think I cleared out the soot pretty well on that run and have limited my driving to 30+ mile trips since then with no issues so far. I have tried to tell when Re-gen is working but I am not that sensitive I guess...my sense of smell and hearing is shot. I can tell by when my fuel economy drops of though. it usually drops 5 MPG for the first part of my 100 mile trips to my daughters place, then creeps back up to 23-24 MPG at the end. same thing happens coming home. I don't like that the Re-gen ruins my fuel economy and wish I could delete the DPf/Cats, and put on big pipes. I bet I could get 25+ MPG that way. You guys that only get 12-15 MPG must drive like you stole it. I rarely drive faster than 65 on the freeway, and usually hold it around 62 and let it drop to 59-60 going up grades.
Don't know how to put on any exhaust brakes? You talking about a Jake brake like on big rigs? What would that have to do with emissions anyway?

 

[tommyturbo]

Thanks for the details. I have not had the DPF warning (80%) display, since I drove to Colorado in June hauling my other car in the bed. I think I cleared out the soot pretty well on that run and have limited my driving to 30+ mile trips since then with no issues so far. I have tried to tell when Re-gen is working but I am not that sensitive I guess...my sense of smell and hearing is shot. I can tell by when my fuel economy drops of though. it usually drops 5 MPG for the first part of my 100 mile trips to my daughters place, then creeps back up to 23-24 MPG at the end. same thing happens coming home. I don't like that the Re-gen ruins my fuel economy and wish I could delete the DPf/Cats, and put on big pipes. I bet I could get 25+ MPG that way. You guys that only get 12-15 MPG must drive like you stole it. I rarely drive faster than 65 on the freeway, and usually hold it around 62 and let it drop to 59-60 going up grades.
Don't know how to put on any exhaust brakes? You talking about a Jake brake like on big rigs? What would that have to do with emissions anyway?

steeve. The key to keeping emissions healthy is to know when the dpf is "cooking" like a self cleaning oven. This happens quite often. My driving
is mostly 10 minute commutes, pick-up and delivery, take outs for lunch, errands, grocery, shopping, all short runs in city traffic when the engine does
not warm up enough. It's a daily driver and grocery getter primarily with a few RV tows a year. I do have analog gauges installed and I know at the
very moment heavy regen starts. You could also add a digital dash gauge easy enough to see this. Once you know its in heavy regen, that is the time
to extend you drive time even in stop and go traffic if you can. If not, let the turbo cool down before shut down and plan to drive again at least 20-25
minutes over 35mph to "cook the soot" out. For me, this heavy regen happens as often as twice in an hour. The dpf builds up soot again and
again. I just let it do it and make sure the heavy regen is complete before shutting down. I cannot tell of the passive regen that happens
in between which is more subtle. The truck runs fine and strong anywhere. You have a standard factory exhaust brake stock. The switch
is to the left of the power rear window. I suggest turning it on every start up except driving in snowy or slick roads. That will keep the vanes
exercised in the VGT turbo. It's where soot builds up and has been known to stick and cause boost problems that causes fuel, air and emission
problems. Even if you don't think you need the EB, use it any way. Your brake pads will last longer. A stock truck like yours commonly only gets
17.5 mpg highway on a good day, so I am impressed with your 23-24. I have heard the heavy regen takes as much as a half quart of
fuel sometimes. No wonder the mileage is so poor. Looks like you have no problem driving unloaded highway but for around town
you could still entertain the installation of a programmer for engine efficiency and economy over the intact emissions. My set up
is proof of a comfortable system that works very well all around. You are welcome to PM or phone me for any details. If you are ever in SO CAL,
stop by and I can show you a good looking, good running, hot grocery getter with emissions intact '08 that will blow your socks off!
Regards,
Tommyturbo

 

[tommyturbo]

Thanks for the details. I have not had the DPF warning (80%) display, since I drove to Colorado in June hauling my other car in the bed. I think I cleared out the soot pretty well on that run and have limited my driving to 30+ mile trips since then with no issues so far. I have tried to tell when Re-gen is working but I am not that sensitive I guess...my sense of smell and hearing is shot. I can tell by when my fuel economy drops of though. it usually drops 5 MPG for the first part of my 100 mile trips to my daughters place, then creeps back up to 23-24 MPG at the end. same thing happens coming home. I don't like that the Re-gen ruins my fuel economy and wish I could delete the DPf/Cats, and put on big pipes. I bet I could get 25+ MPG that way. You guys that only get 12-15 MPG must drive like you stole it. I rarely drive faster than 65 on the freeway, and usually hold it around 62 and let it drop to 59-60 going up grades.
Don't know how to put on any exhaust brakes? You talking about a Jake brake like on big rigs? What would that have to do with emissions anyway?

steeve. Did you buy your '08 thinking you would just drive around as usual like a gasser pickup? Did you expect an HD diesel to return better mileage too? These
HD diesel pickups after '07 have changed probably forever. The modern HD diesel pickup is nothing like previous generations as far as economy but capacity
and towing ability has increased. Add EPA smog stuff they also get more complicated. These HD diesels are made to work and tow hard and not putt putt around
like I do most of the time. My last truck was an '03 2500 5.7 gasser which struggled up hills. I bought the CTD mainly for those towing trips and the
rest of the time a grocery getter. I probably felt just like you, really bummed out about the CA smog stuff. Horrible mileage compared with other makes.
However, I did buy it for towing and not mileage so I though the poor mileage just went with the territory. But it did tow so well. It was a keeper anyway. It was the first two years that I studied all I could find about what to do about the awful emission system but in CA not much but just to keep emissions healthy.
Then I found a programmer that really helped in efficiency, mileage and towing with mileage better that the gasser. Even though I didn't buy the CTD
for mileage, I was pleasantly surprised with the gains. I'm a happy camper. If short run mileage really bugs you then you should continue with what
you are doing with using the economy car and only use the '08 for longer rides. That sounds perfectly o.k. For me it's an everything truck. Some other responses about the emissions intact were pretty harsh and I can understand that. It was that I was determined not to let the EPA ruin my day. Now my CTD is running even better that most any other modern HD diesel no matter what smog stuff is on. If pickup mileage is that important, you might look into the new crop of half
ton diesels out. Looks like a consumer trend.
Another windy $.02.

 

[steeve]

Again, thanks. Here is a pic of my other car that fits in the pickup bed. I am in So. Cal. (Ramona)...where are you tommy?. I would be interested in one of those programmers if they are not too pricey and they would improve fuel mileage on my stock setup. I would not want one though if they interfere with passing smog tests.
Location of the Jake-brake as described "next to the rear power windows switch"? I have no rear windows, power or otherwise, so where is it? I have an automatic trans too, probably a six speed...hard to tell tho; no owners manual.
I got this truck because my friend has an earlier version 2001 5.9 L that I was very impressed with. I expected great fuel economy like his got (21+) and long engine life too. I just like diesels. used to own an 85 Chevy diesel V8 4X4 that I used for many trips to Baja. My last truck was a Toyota 4x4 gas 4 cylinder, which was very cramped inside for my height and got terrible fuel economy for a light 4 cylinder truck. The Dodge/Cummins was a big step up in performance, comfort, and fuel economy for me, although I did have to change out the Diff carrier bearings right after I got it; the PO had a heavy service box on it. Still need a trailer hitch, complete front bumper and tailgate hardware for the used, bare tailgate that I found. which was all missing when I got it. The hood had been replaced after a front end hit by the PO, and the intercooler was smashed in too, but it ran well. I already bought a new core support bar and replaced the intercooler, fan clutch, and AC compressor, so I have about 9K invested in the truck now, including purchase price. If I start having serious problems, knowing what I know now, I will probably get an older model; pre-smog 5.9. that is cheaper to maintain.