Engine/Transmission (1998.5 - 2002) Mileage--has anyone really improved it?

[geusterman]

I am getting discouraged. My 2002 4x4 6spd 3:54 has never been above 14 mpg. OK, so the front diff is full-time. I have a Gear Vendor and 19. 5's/245 Michelins. I cruise 70 at about 1300 rpm. Still 14 ish with mileage percent for speedo error and 11 with my BigFoot Camper. Oh yeah, same mileage with or without my Edge EZ. There are 12,000 miles on the truck. Sigh... . Anybody ever adjusted fuel or SOMETHING to improve mileage? I was hoping for at least 20 with the gearing/tires etc. Might as well have a Chevy... . geusterman

 

[lmills]

Dang, their has got to be something wrong. I do better than that with my auto and 4. 10's. I never drop below 16 empty, never checked while towing, but my guess is about 11-12. I have seen as high as 20 on open road cruising.



Has it ever been to a dealer to be checked?

 

[Steve Campbell]

geusterman....

do you have a Pyro? It amazes me the difference in EGT by running the engine "too slow" -vs- in the sweet spot. 1300 RPM's seems slow unless you are on very flat or descending ground.

 

[StephenThomas]

Mileage Improvement

I average 17-18 mpg in stop and go around town with a lead foot. On highway, I'm getting an average of 22-23 mpg. Towing my 5500lb trailer, I average 12-14 on the highway depending on road conditions. The best thing I ever did to improve mileage was the addition of Diesel Dynamics True Torque Power Module. As my wife said... . the module has paid for itself in gas savings.

 

[fox]

Your truck has something wrong. Have you changed or checked the Intake air temp sensor and the manifold air pressure sensor?

I bet it will inprove with more miles on it. And it will most likely do better at 1600 to 1700 rpm.

My 02 auto 4x4 does 16-21 depending on the fun peddle position.

Also 275 injectors was the best mileage inprover I tried.

Do a search on the Intake air temp or manifold air pressure sensors and get some info. I think it was Marco that had some good info.

 

[jtisdale]

A lot of things are to be considered. Driving habits, tire pressure, speed, load, grade of fuel, boost and egts as mentioned above, etc.

My mileage didnt start improving till I came close to 20,000 miles. Also, everything I added performance-wise, has helped with mileage. Heck, I didnt get over 20mpg until I put the III's in. Now, its never less than 19 empty, and never less than 16 loaded (17,000# gross).



I would get your fuel pressure checked, if you havent done so already. Check the IAT and clean. Check tire pressure. Keep the rpms around 1900-2000 when in tow, and no less than 1600-1700 empty. Keep speed below 70mph. I have found my truck gets better mileage at 60mph than it does at 50mph. Drive with a feather foot.



Disclaimer: If none of the above works, put another 15,000 miles on your truck, and repeat.

Good luck.

 

[geusterman]

You guys are great. I run about 1500 to 1600 in 7th because I speed. I have no cruise but I am a very careful experimenter. I have held lower speeds for full tankfuls but the results are poor. You would just think that a Cummins with these long legs would be a dynamite mileage machine. The big question--do I have to go to the dealer to check the factors mentioned above? (I have no EGT yet as EZ is soft on the heat and I watch water temp which rarely moves past center, even those long grades up the Columbia Gorge with the camper and headwinds). Fuel pressure is fine (checked on last trip at Cummins shop and they had no ideas for improving mileage). Is it just the full-time front end without a disengagement box?



The mileage has always been this way. Bill Heath at Heath Diesel Performance (or whatever he is calling his biz these days in Ellensburg WA) makes a 400 hp mod with stock injectors and modded turbo and they get 24 mpg at highway speeds. THIS WAS ONE OF THE MAIN REASONS I SOLD MY CHEVY DIESEL AND BOUGHT A DODGE! AAARRRGGGHHH. OK OK Ok ok ok. I'm ok. Oooohhhhhhhhmmmmmmm. So do I need to rip off my EZ and go see a dealer? George Eusterman

 

[RobbyRam]

If you get DD2'S and an 'EZ', you'll get in the 20's, I guarantee you!

Bob in Sacramento

 

[geusterman]

Hey Bobby Ram, what were you getting before? What are DD2's. George Eusterman

 

[KL]

These trucks are not very aerodynamic. Once you go over the low 60's your mileage will start dropping, even at low RPM's. I think 1300 is below the engine sweet spot for the 24V. Good luck. KL

 

[RobbyRam]

geusterman,



DD2's are 'Diesel Dynamics Stage 2' injectors. They run approxamatley $500, and the 'Edge EZ' box about $650. (Buy the Edge Comp box for about the same price but just don't hook up the 'wire' to the VP44)

Your power will increase to the rear wheels from about a dynoed 170hp to 270hp, but the biggest surprise will be the milage increase. 13 avg mpg's to 18 avg mpg's. The reason, I think, is that you barely now have to push the 'go pedal' to get to 65mph.



I actually even increased hwy mpg's to over 23 mpg's and have witnesses to prove it! For example, I drove , on one tank of diesel, which was measured less than 33gallons, from Sacramento to Bishop CA over Monitor Pass to Hwy 395 and even drove around for two days in town and then drove all the way back to Sacramento on the same original tank of fuel with diesel fuel left over! That's over 620+ miles on one tank, going up mountains twice to boot! Before the mods, I had to fill up in Mammoth on the first way.

My truck rocks... when it's running

Bob in Sacto

 

[jponder]

Re: Mileage Improvement

Originally posted by StephenThomas

I average 17-18 mpg in stop and go around town with a lead foot. On highway, I'm getting an average of 22-23 mpg. Towing my 5500lb trailer, I average 12-14 on the highway depending on road conditions. The best thing I ever did to improve mileage was the addition of Diesel Dynamics True Torque Power Module. As my wife said... . the module has paid for itself in gas savings.

Are you a manual ? This is something I noticed before and mentioned about the 2001. are you a 2001 or a . 5? It seems like the 2001 ETH/DEE get exceptional mileage. Above and beyond the 2000. 5 and previous models. There are few other groups that can get 23 MPG empty. newer models that is

 

[geusterman]

Robby Ram--so you personally went up from 13's to 18's with the DD2's? Thanks in advance, George

 

[geusterman]

And just so you all don't write me off as a leadfoot, I got 21/22 in my 83 Blazer 6. 2, 14/15 in my 93 6. 5 K2500 and I get 44. 9 in my 98 Jetta TDI. Normal mpg's here. And 14 in my Cummins. Since day one. Also Robby, I already have an EZ.

 

[RobbyRam]

Get DD2's! You'll be blown away by the power and milage difference.

Bob in Sacratomato

 

[Ncostello]

I'd be going to a Cummins dealer and getting some kind of diagnostic work done. Before I personally started adding expensive injectors and boxes, I'd be wanting to know why its doing so poorly stock. 1300 is too low for I think. I get 20 easy in 5th with no load and rpm's turning 1800-1900. I've checked this many times. Lower rpm's isn't always the best. These engines will run all day at much higher rpm's and its probably better for them for mutiple reasons.



I think it was Illflem (could be wrong) who once stated his best mileage occured pulling in hills while mostly in 4th. The engine was singing high notes most of the time... but thats the point of the "sweet spot" efficiency range when working. Torque gets you moving, HP keeps you moving. Get those R's up in the horsepower range. Just my opinion.



Something is wrong and performance parts probably wont fix it. It should do better on its own.

 

[geusterman]

ncostello--I agree that there is a "root" problem. I will search air temp sensors etc. If I went to the Cummins people would they tell on me re my EZ or should I remove it? George

 

[LoneRam]

My .02c

geusterman,



Just thought I would jump in on this. I have hand calculated every tank since new. I started on two quests: Mileage and Style. Both have led me through some $$ but I'm happy with where I'm at so far. Anyways, stock my mileage was around 15-16(keep in mind I live on an island and am always doing the stop and go thing). I then went through the box, injectors, turbo, transmission expecting to see some "improvements" like everyone else was seeing. While my mileage appeared to remain the same, my power doubled. In the middle of all this I added 35 inch tires and a leveling kit. I tried the 180 degree thermostat and high tire pressure along with synthetic in both diffs. My mileage was now 13-16 but with a taller and much faster truck. So I guess my "mileage" did increase if you don't count the way I now drive and the larger truck I push through the wind with the bigger tires. My only noticable improvement came from switching to a full synthetic engine oil. The next tank was 1. 5mpg better than I had been getting and it continues to be at least 1-1. 5 mpg better than before.

After the dealer turns you away, and your ready, that would be my first mod(after the odometer was around 10-15k)

Good luck



Loneram

 

[StephenThomas]

Lone Ram

Lone Ram...

I used to live in Hawaii... . in fact, I still have a home in Makakilo. Anyways... with the type of traffic you deal with on a daily basis out there, I'd say your mileage is pretty darn good!



On another note, I don't remember too many diesels out there on those islands. The local boys probably don't know what to think when they see... errr... . hear you coming!!

 

[Hohn]

DD2s and EZ is a great combo. Just over 2K on mine, and it's great.



Sell your GV. With the 3. 54s you don't need it. All it does is increase load on the engine (taller gears) and move the rpm down out of the efficiency range. (see EGT for proof)



2K rpm is the optimum on these engines. It's no mistake the 2K rpm in 6th (w 3. 54) is just over 70 mph.



There's no reason you should NOT be getting near or over 20 when empty. Unless you drive too fast (which MAY happen with the dd2s!!)



1) sell GV overdrive

2) Lose the large 19. 5 inch tires (higher rolling resistance and more weight)

3) Clean IAT sensor

4) Get RV 275 injectors or DD2s, depending on budget

5) get lighter foot



I GUARANTEE THAT THESE THINGS WILL INCREASE MILEAGE!!!!!!



HOHN