I have a 04.5 CTD with 20,000 miles on it…
It only gets about 15 MPG on average not towing (70% freeway) and here are my reasons, I think

Obviously the motor is not completely broken in, and I run it on the Juice pushing 37’s. All that aside, I think it is more of a factor of the exhaust and tyranny. The tyranny is $hit!! (It’s an auto)

I know a few people with the same exact truck and they drive very similar to me and are getting 20+ MPG…

Here’s what I left out, my junk is straight piped and I think that this is why my mileage is in the tank. Originally I have heard that diesels like to breath and are not as sensitive to back pressure as gas motors. Is this true, do you think this is my main MPG factor? I am looking for 5 MPG here, not a small amount.

I really like the way it sounds… and pissing off my neighbors is fun too, but is it time for a change? And yes I know that Mileage has been discussed here many times, I want to hear about people that changed their exhaust.

I don't think the straight pipe is hurting your mpg at all.... it's more likely the 37's than anything.

And it's not broken in yet.

As Mechanos said, its probably your 37s.

FWIW when I went from straight pipes to 4" MBRP exhaust I saw no change in MPG.

I used to have an 04 (305/555) with 4wd, auto, quad cab, 3.73. With cruise at 70 mph I would get 19-19.5 mpg reliably. 16 mpg city... On a regular commute mix of about 70 city/30 highway, I'd average 18-18.6 mpg.

I think it's your tires - as well as the added wind resistence from height.

has your speedo even been calibrated for the new tire size?

Are you using the mileage computer to check mileage (or are your friends?) or are you figuring it by hand? (miles driven divided by gallons to refill)

Turbo'd motors need ZERO restriction in the exhaust syste. Straight piping should never affect mileage for a negative provided its as large or larger than original...

Non-turbo and supercharged engines require zero backpressure to make max power but they do need exhaust VELOCITY to perform well... This is where the misunderstanding lies with haveing too large of an exhaust system on a non-turbo motor....


Chris:cool2:

I hated my straight piped 98 12er...it would resonate at 70 mph and drown you out...

I call bull shit on every one of you that says the straight pipe didn't affect mileage!!

Mine went way down, but it was because I could keep my foot out of it!! :flipoff2:

But seriously, between not being broke in and the 37's, you will get crappy mileage. And your auto isn't helping any either.

Ive been straight piped for over a year now, and I noticed no difference in mileage, unless I get on it bad. its the 37's and the slushbox.

3rd gen dodges just don't get the mileage that the earlier ones do. I average about 15mpg on mine with 22K on the clock.

I have a 04.5 CTD with 20,000 miles on it…
It only gets about 15 MPG on average not towing (70% freeway) and here are my reasons, I think

Obviously the motor is not completely broken in, and I run it on the Juice pushing 37’s...

I know a few people with the same exact truck and they drive very similar to me and are getting 20+ MPG…

Here’s what I left out, my junk is straight piped ...
I really like the way it sounds… and pissing off my neighbors is fun too...

I've got an '01 w/220,000 on it.
when I drive it, I avg. about 16,
when my wife drives it, she gets about 20.

I didn't think we drove that much differently, until I did the math.

It's probably a mix of three things: 37's, low miles on the motor, and you're driving more aggressively than you think. Once you get the motor over about 1800(about 70mph), the mpg drops.

has your speedo even been calibrated for the new tire size?

x2
Also, 15 with 37's is normal.
Most with stock size tires get 18-19.

15 mpg on 37's aint bad at all.

15 mpg on 37's aint bad at all.

IIRC, your truck has a 4 inch exhaust stock, shouldn't really be an exhaust flow problem...

straight pipe will help lower egt's...sounds damn cool too. will not be noticable mpg difference. other trucks w/ more restricting stock exhaust...yes, but yours....no

As a general rule...

I assume anyone claiming 20+ mpg scored well below me on the math portion of the SAT. :flipoff2:

fyi, my 12v with 33" tires, 5spd, 4.10 gears only sees 15mpg with hurricane force winds on my back. My '03 6pd, straight piped with stock dually tires saw 17mpg on a good day... but rarely. It was quadzilla boxed though... and was throttled happily and often.

I should have mentioned that it has 4.10’s and my friends that have the same truck on 37’s have 3.73’s. Also, my spedo is not calibrated, but I add about 20%, and this is using the computer read out, and me figuring it out form the mileage. I was thinking that with those gears the 37’s might help on the freeway to keep the RPM’s down.

Anyways, I am aware of all the other factors…
The point that I was making, and thanx for answering, is the straight pipe. Looks like I’m not going to make the effort to do anything but drive it for now.

oh ya, i am fighting my EGT, that is the other reason for the straight pipe

I'm guessing your fishing for more fuel millage, correct?
How hard did you work it after the first 500 miles? This is the time when guys work the living shit out of their motors to get them broke in, if you didn't don't worry it just means your motor will take longer to break in.
Also once it is fully broken in you'll only pick up 1-2 mpg on average.
If you want more MPG try adding air intake maybe a programmer. There plenty more you can do, just something for you to think about.

I agree with you there.

On average I get 16mpg with my truck. 98 24v, 4.10s, 35s. I have gotten as high as 18mpg doing all highway driving before, that's it though.

Sorry, but a 7000+ lb brick isn't going to get the same mileage #s as a 2500lb Honda and I have no idea where people think... oh that's a diesel, you must get like 30 mpg with that huh??

Had a guy at work try telling me he gets 35mpg with his 7.3L Excursion pulling a car hauler.

About the best fuel mileage you can get would be from a 2wd, stock tires, highway geared truck. I have heard of those setups getting in 20-23mpg range (CTDs)

As a general rule...

I assume anyone claiming 20+ mpg scored well below me on the math portion of the SAT. :flipoff2:

fyi, my 12v with 33" tires, 5spd, 4.10 gears only sees 15mpg with hurricane force winds on my back. My '03 6pd, straight piped with stock dually tires saw 17mpg on a good day... but rarely. It was quadzilla boxed though... and was throttled happily and often.

my spedo is not calibrated, but I add about 20%, and this is using the computer read out, and me figuring it out form the mileage.

.

So your guessing...........

Go into the dealer and get the damn pinion factor set to get your speedo correct.
Even if they charge you, its only going be 50$ ish.

I had a 97 CTD 4x4 with an auto and 4.10 gears, it got around 15mpg on average with highway and city driving. I now have a 95 CTD 2wd auto with 3.55 gears and I can get 20-23 on the highway no B.S. In my experience the gears and the fact that it's a 4x4 make a huge difference in mileage reduction on these. I liked the way my 4x4 looked a lot better but I sure enjoy the additional mpg of the 2wd.
And those 37's aren't doing you any favors either! You can be bling or you can get smaller tires and get better mileage. Go with whatever is more important to you I guess.

I have a 12v and a AT in my F250 with 35" MTs, was getting 15 mostly highway with the 4.10s. Switched to 3.54s and getting 16.5 under same conditions. I plan on more tweaking for economy, but the gearing made a 10% difference.

Yup.... those 37s are killing you. I have 35s on mine (with a straight pipe). I average just over you at 15.75mpg. I have gotten as much as 18mpg, and I average in the 12mpg range while towing a 7000lb trailer.

I also have an Edge HOT Juice, intake, and an upgraded lift pump.

Yeah, the straight pipe shouldnt be hurtin your mileage. When i straight piped my '01 i saw no change in MPG.

I would vote the tires and lift are what is killing your mileage, im not too sure about the slushbox tho. I averaged 21-22 mpg with my truck (unloaded) on the freeway with no mods except an Edge comp and the straight pipe on my auto.

Just go get yourself a nice 4" exhaust from MBRP or silverline. The truck will still be nice n loud outside, but the difference in the cab is very nice. Much less drone.

05 610 CTD w/ 40,000 on the ticker. It's been straight piped for about..........39,990 miles of its life and I get about 16-20 round town or towing (if my foot lets it)and 20 solid not towing on freeway:flipoff2: BTW :bone stock everything

As a general rule...

I assume anyone claiming 20+ mpg scored well below me on the math portion of the SAT. :flipoff2:

fyi, my 12v with 33" tires, 5spd, 4.10 gears only sees 15mpg with hurricane force winds on my back. My '03 6pd, straight piped with stock dually tires saw 17mpg on a good day... but rarely. It was quadzilla boxed though... and was throttled happily and often.

Hmmm, never took the SAT. Maybe a genious such as yourself can do some math for me. Filled up my 97 12v (5spd, 4.10s, 35" tires), drove a known distance of 100 miles (over a mountain pass, btw), and topped off before heading up in the sticks. Truck used 5 gallons. What mpg is that? :flipoff2:

Hmmm, never took the SAT. Maybe a genious such as yourself can do some math for me. Filled up my 97 12v (5spd, 4.10s, 35" tires), drove a known distance of 100 miles (over a mountain pass, btw), and topped off before heading up in the sticks. Truck used 5 gallons. What mpg is that? :flipoff2:

Looks like we should work on the non-math portion for you first. :flipoff2:

As a general rule...

I assume anyone claiming 20+ mpg scored well below me on the math portion of the SAT. :flipoff2:

fyi, my 12v with 33" tires, 5spd, 4.10 gears only sees 15mpg with hurricane force winds on my back. My '03 6pd, straight piped with stock dually tires saw 17mpg on a good day... but rarely. It was quadzilla boxed though... and was throttled happily and often.

Your problem is obvious - 4.10 gears in the axle. I also wonder if you have a 4wd. I had that same truck and couldn't get more than about 15 mpg. However if you try a 2wd with 3.55 gears you will see over 20 mpg on the highway. Come out to Cali sometime and I'll prove it to ya!

Your problem is obvious - 4.10 gears in the axle.

Well no sh*t! :flipoff2:

However, I've had two 24v and now this 12v, some a 3.54, a 3.73, and this 4.10... I've got several friends with all flavors of CTD, 12v, 24v, 4x2, 4x4, srw, drw... you name it... we all do a variety of in town, highway, towing non-towing... and most of them run stock setups including the tires... none have ever seen 20 mpg. It's always between 15-18mpg non-towing.

Besides... everytime I head towards Kali... I usually wind up in Moab... you'll just have to send me a postcard. :D

2004.5 CTD 325/600 4x4 quad cab auto 3.73 45,000 on the ticker. I picked the truck up second hand with about 20k on it, bone stock. It saw 12.5-13 combined city/highway. At 30k something big changed, enough I took it in to get looked at. The engine began to sound a bit different and started to add up the milage. After 30k I saw 13.5-14 on the same combined driving, no problems noted by the dealer. At about 35k I added a Volant intake and water sock and had the cat deleted and high flow muffler added. I stuck with the stock 4" from the turbo, just took out the cat, new muffler and 4 inch stock out the back. I did not see any in town change other than a bit more power, but the highway milage went up to about 18. At about 37k I added a TST powermaxcr. This was this single best add on, but maybe because I already added the exhaust and intake. With fresh filters on its maiden run, I saw 24mpg highway. This was on the recommended 3x3 setting. It was a 30 mile round trip to the next town and back on the same road. I prefer to run the torque setting at 9 and the HP at 3 now for best milage and plenty of getup. With this setup, I saw a consistent 19-20mpg highway and more like 16.5 city. I often tow a 7000lb trailer at a 2-3mpg loss. At 44k I had a 4.5" lift put on and added 35s. Milage went down to about 19 highway and 15 city. I took the TST off two weeks ago for the 45k service and to have them look at a noise I was hearing in the engine. No problem with the noise, but the milage has gone down to about 17 highway and 13-14city. I have a combined milage now with 35s, the intake and exhaust of 15.5.
Needless to say, the TST adds both milage and power and will be back on as soon as the rain stops. I should see a combined milage of no less than 16.5 with it back on. One thing I would like to add is that the stock trip computer is not aware of the added fueling of most programmers. This means it will display a better milage than you are actually getting. Do the math and check it for real, not by the computer. Also remember to take into account the added tire diameter because you are really going farther than the odometer says.

I have a '92 CTD and I got 20.1 MPG using a GPS unit on last long trip..

I drove from NC up to Mountains of VA and back.

Truck only has 3200 spring and straight exhaust.. Truck was empty with bed cap on it.. SO Yes some of these trucks can get good mileage..

Now I do not get that everyday but I did on the road trip..

... I get about 16-20 round town or towing (if my foot lets it)...

The jetski doesn't count. :rolleyes:

in my experience highway gears are the way to go. Used to have a 01 dodge 4x4 with h.o factory motor and 6 speed 3.50 gears. With a Banks Power Pack set on offroad level, exhaust brake. Used to get 18 at @ 75mph empty. At 25,000+ lbs total pulling trailer have gotten 14mpg @ 60mph usually around 9 at 75mph. I would get speedo corrected for tire size this should help. Many control boxes do this and you get more hp. I agree with putting muffler in exhaust. still sounds great but with less cab noise.

My 02' HO six speed with 285's and 3.55 gears with a camper shell gets an honest 18 mpg on the freeway if I set the cruise on 70 mph. The speedo is recalibrated, and I hand calculate my mileage. Towing mileage ranges from 11-13 mpg at 60-70 mph. It has 63k miles on it. I have a 4" straight pipe exhaust on it with an AFE stage 2 kit on it with a pro guard 7 filter. I've had a straight pipe for about 40k miles now, and I am tired of the noise. Also, my wife and I are moving into town, so I am going to put a aeroturbine muffler on it.

My 03 6sp 4x4 jot about 19-22 mixed driving empty14-16 towing. I ran a 100 hp quadxilla with 4 " exhaust and an AFE stage 2 kit on it with a pro guard 7 filter.
On my 06 Mega cab 6sp with 100hp chip 4" exhaust with stock intake Im around 15-18 with stock tires with 19000 miles

Just to throw another word on mileage. My truck is 2wd. 24 valve. I have many after market performance parts.
I figure my mileage at every tank. The way you drive your rig really matters... I can average any where from 16 to almost 20 per gallon. And can really tell when I've been hammering on it. And the trip computer is always off by about 2 mpg's.
And I have never seen above 20mpg's evan stock.

Those tires are killing you.

I think if you did get an intake and free flowing exhaust it may help. But not alot....