Hi to everyone. This is my first post,been lurking around here for a few weeks.Been doing alot of reading and have learned much.This is my first diesel and am very ignorant when it comes to them.I bought the Ctd on a recommendation from my brother who has a 98 and has been very happy with it. His best mpg is around 21 on the highway but he said he has two friends that have new ones and were getting 25 mpg. After all the reading on different forums I can see that this was BS.For the most part I am happy with my truck.I am a little unhappy with the mpg. I seem to be doing better than some of you but i was expecting to get better than i am.Currently I'm getting 19.4@70,
20.3 @65, 20.8 @ 60, and 16.3 around town hand calculated.What do I need to do to get 25mpg and be able to drive 75 0r 80 mph on the highway? The only towing I do is my motorcycle once in a while.

 

more than likely you will never see that unless something out of the blue happens. Be happy with what you are running right now that sounds pretty good. If you free up the exhaust and the intake you will see maybe 1-3mpg possibly more. You can also get a module such as the quad xzt or ez edge but don't go to drastic with the other ones and you could see another 1-4mpg. This is all claimed though. I am sure someone else will chime in on their mods to let you know on what they did and if it helped but I personally would start with the Muffler and the Intake then go from there.

 

I think that 25 is unrealistic, I think that anyone who is totally honest would be very happy with 19. If you are like me, the more mods you do for fuel milage end up being a wash because they are so much fun to DRIVE.

 

man if i could get 16.3 around town i would be estatic...im only seeing low 12's...and thats barely letting the truck see 2,000rpm

 

so far im seeing a good gain in mpg after getting my stock injectors honed by the guys at Dynomite Diesel. Plus the truck runs smother than it did with 10 miles on it and it makes about 70 more hp. If all your lookin for is mpg gain then get them honed to maybe 50 hp. Youll love the way it runs after they are done. Im super happy I did it.

http://www.dynomitediesel.com/

tell em Randy sent you.

 

First, I have an 03, SO Auto w/47RE Tranny. The first thing I did was to install a homemade torque tube, ( not butt ugly ). The stock has a lot of restrictions. They sell them on ebay and other web sites for $92. Mine cost $34. Next I installed a Flo-Thru muffler. That gave me 3+ mpg. Then installed an Edge EZ, set on level #3. All this added about 3-4.5 MPG. Anything you can do to help the intake and exhaust will give you more MPG. The torque tube will give you quicker turbo spool up. Javahjoeo from Kokomo

 

I would think that 35 inch tires would help, because they would reduce your RPM's.

 

i have taken the baffles out of my torque tube by cracking it apart on the end where its glued together. then they just slide right out and you glue it back together with two part epoxy........i just did that for flow wasn't thinkin about mpg at the time. I have 4.11 gears and a six speed and if i kept the rpms at 2000 or lower ....thats 64 mph i could get 19 mpg. but after looking at a picture of a rokketech i decided to buy the sensor and modify it myself and after doing that i can drive 80 and with a heavy foot and always get 19 mpg. i am in the process of recieving a 5" exhaust and as soon as thats on i will be working on the "bhaf" and im hoping that will put me up a couple more miles per gallon. 21 would make me stop trying for more.

 

I have wrestled with the mpg devil for three years now. To sum it up in writing these trucks are heavy period. 7000 plus pounds takes fuel to get it moving so stop and go driving and idle time kill mpg. The best I've achieved was 21.24 mpg running 62 mph empty. The worst was 13.11 towing 8900 lbs trailer on the I-5 Vancouver to San Fran. All these calculations were performed by topping up (painfully slow) filler neck. I have given up driving for mpg as all it does for my rig is carbon up the injectors. This motor is a medium-duty industrial strength engine that is designed to work! I know what you thought, I'll buy a diesel and get great mileage! Ya but the physics of moving a 7000 lb truck doesn't change. Listen people always pad thier figures and filling a stock tank to absolute full leaves a huge margine of error. So at this stage of ownership I drive the bejesuses out of it and regularly max out my boost at 24-25 psi and pyro 1250-1300. Any joe blow wants to play I'm game and I can tell you I'm having a ball. So still keeping track of mpg I get 17.5 - 19.2 driving a 7000# 3/4 ton 4x4 ( on winter diesel!) like it is my middle aged sport car. If I wanted economy I would have bought a VW Jetta

 

If you think 25 mpg is BS - I have a friend who claims his 03 gets 30 since he got the EZ and his OH puter is dead accurate.

 

Welcome to the forum ! Man I think you are doing pretty well ! I would not touch a thing for now. Your mileage is likely to increase a bit once you get some miles on her...

25 mpg.... that's horse (&*^%$ Maybe going down hill, in neutral with a 50 mph tail wind !!!

My truck gets between 17.5 to 20 hwy empty running @ 65mph.

Keep in mind also that these trucks seem to have a sweet spot. Drive much over 1800 rpm and your mileage will go down...

 

Purchase a programmer that can modify the trucks computer. It would be a good idea to make sure the programmer you choose will also recalibrate the speedometer with different tire sizes. When you replace your tires in the future, buy a tire that is only 1 or 1.5 inches taller than the stockers. Most vehichles powerbands are set to perform their best at 55mph on the highway. The programmer should boost your power while the tires should lower your engines rpm's. This means 1800 rpm for 70mph instead of 2200 rpm for 70 mph. This does not mean the taller the tire the better. For example, a 35 inch tall tire would drop the rpm's to 1200. (which is too low for the highway). Your max torque is around 1700 rpm's. That is why stock 3rd generation dodge diesel trucks run 55 mph at 1800 rpm's. (or there abouts). Also, get more air to the motor, inside and out. Also,open the exhaust up. I would recomend purchasing good quality performance products with warranties. There are many ways to achieve your goal, It can all be solved with logics and math. Taller tires will rotate less per mile than a shorter one will, but it will lower your rpm's out of its peak highway performance powerband. This is why you need the programmer,cold air induction and high flow muffler. To make the engine capable of doing the same work it did at a higher rpm at a lower rpm. Tires rotating lesser times a mile while slightly lowering your rpm's will get you really close to that 25 mpg goal.

 

I am totally conviced the mileage #'s all over the place between similiar trucks is due to fuel quality . I just tried an experiment and dumped 2 bottles of Stanadyne Perf Formula in a tank at fill up and WOW !!!! My dually has 25,000 miles now and mileage has jumped up and throttle response is way up also . My truck is bone stock except for an AEM intake and a free breathing set of duals and she idles like a gasser . I pulled out into traffic and hit her hard and left a 3rd gear scratch without even trying ......... AND I had @ 1000 lbs in the bed !!!! This seems to be the "Holy Grail " for MY truck but it sure is worth a try !

 

When running 70-75 empty I get about 16-17. When running 60 I seem to get 20-21 mpg. But when I run 60 by the time I get where I am going I done forgot why I was going there in the first place.

 

Check my sig, I'm running an '05 Auto 2WD QC. Totally stock. Just filled up today with my best tank to date, 20.97 hand calcluated. I use the same station, same pump, fill to the same level each time. To get that kind of average you have to baby the throttle, I mean baby it. I get nasty looks all the time from people passing me just after the on ramp on I-95. I run 68 on the highway, puts the Cummins at 1900 rpm. In heavier traffic I bump it down between 62 and 65. There are also a few roads in my travels where I have to run 5-6 miles at 35 mph with no lights.

At 68 I get 21.5, I have seen 23 right after a fillup and running 45 to 55. Stop and go kills the mileage instantly, idling kills the mileage. I'm with the others here, it's a 7000+ lb truck. 19-20 mpg is awesome. My '85 Corvette go fast machine barely makes 20 mpg.

Ryan