My 05 Dmax is getting about 16 mph hwy at 75 mph. Unacceptable. My 04.5 weighs a bunch more (~1000lb) and gets 17-18 at 75-85. Both trucks were "fresh" when I drove them long distances. First thing that comes to mind is tire dia, but I saw something interesting yesterday.

I put a 04.5 flash in my 05, and it indicated better mileage on the DIC, and by fuel gauge estimate. I'll need to do some "hand measured" miles to back it up. I'll report back when I do a long trip with the 04.5 calibration.

McRat;

You are experiencing the same mileage that I have got all along. I hand calc every tank, and have seen 16.3 on very rare occasions. Usually hovers right around 16. I have seen no difference since turning 10,000 miles, as some have suggested, and am fast approaching 20,000 now. My driving mph seems similiar to yours, and I am down in Escondido, just down the 15 from you. Probably similiar road/freeway conditions.

Is your '05 still completely stock? Did you remove the kitty? I would like to see better mileage also.......

Bruce

That's about what I was getting... Until I killed the kitty. Coming down to KY Friday, at the end of my 250 mile trip, the DIC is idicating 18.8, after sustaining speeds of 70-80, primarily around 75.

McRat;

You are experiencing the same mileage that I have got all along. I hand calc every tank, and have seen 16.3 on very rare occasions. Usually hovers right around 16. I have seen no difference since turning 10,000 miles, as some have suggested, and am fast approaching 20,000 now. My driving mph seems similiar to yours, and I am down in Escondido, just down the 15 from you. Probably similiar road/freeway conditions.

Is your '05 still completely stock? Did you remove the kitty? I would like to see better mileage also.......

Bruce

Mileage numbers are from bone stock trucks, a 05 2500HD vs. a 04.5 3500SRW.

The 3500SRW comes with 265 tires, which drops the RPM about 150.

McRat;

Too stupid to figure out how to use the quote feature like you did......

Went out and looked at my tires. They are definately 245's, althought they say 265 on the tire also, just not in the actual size block. Kinda weird. But, all things being equal, if I were to uograde to the 265, it sounds like we would still be getting the same mpg. Or, are you suggesting that my mileage may increase due to the rpm drop? Makes sense, I would just need to calibrate for the change on the speedo due to the larger diameter tire.

Any thoughts on removing the kitty? I'm stone stock currently also.....

Bruce

Your mileage SHOULD increase with 265/75-16 E-Rated road tires if you drive 75. Our mileage is very "rpm dependent". If you can keep it below 2000 RPM, you will get substantially better economy. The "265" on your tires is the model.

Normally engines get their best fuel economy at the torque peak. In our trucks, that's supposed to be about 1600 rpm.

Thanks, McRat. Tires are getting close to replacement time anyway, so I appreciate the input on the 265's. Hard to stay under 2000 rpm at 75 though, huh?!

Enjoy the day.

Bruce

hey guys, i have been having mileage issuses also. my truck has 265s,cat back 4in, cold air intake, and the edge juice. Its an 05. I recently found something to help. I realize you guys are talking about stock trucks but this is worth noting. The tech at edge products told me to run my edge on level five and five ( the two highest settings) if i could drive conservative. I've kept my foot out of it and I'm getting 2 more mpg.

How did you put 04.5 flash in the 05? Swap ECMs or some other method?

ECM swap.

You are going about the ECM swap all wrong... for better mileage you need to swap in a Honda Civic ECM, not the 04.5:muahaha:

Big Blues ECM will be calibrated for 265 tires and casper's 245s. That will make a bit of a difference since you will not actually be going the speed indicated.

Big Blues ECM will be calibrated for 265 tires and casper's 245s. That will make a bit of a difference since you will not actually be going the speed indicated.

Yeah I know. But the fuel needle didn't move much. The DIC says 28.1 MPG right now with a mild tune in it. I need to do it more controlled, but it looks promising. It was drinking like sailor on shore leave before, and now the needle barely moves.

I was pretty sure you were aware, but it is sunday so I thought maybe you weren't thinking clearly. :D

Please forgive my ignorance but..............what is the "kitty"? And how do you kill it?

catalytic converter. Killing it means removing it

My 05 Dmax is getting about 16 mph hwy at 75 mph. Unacceptable. My 04.5 weighs a bunch more (~1000lb) and gets 17-18 at 75-85. Both trucks were "fresh" when I drove them long distances. First thing that comes to mind is tire dia, but I saw something interesting yesterday.

I put a 04.5 flash in my 05, and it indicated better mileage on the DIC, and by fuel gauge estimate. I'll need to do some "hand measured" miles to back it up. I'll report back when I do a long trip with the 04.5 calibration.

I am very interested in how this turns out. The poor mileage has been tied to the overheating very often, and a tuner (fuel timing and quantity) has shown to reduce the problem. Have you towed heavy with the 05? If the 04.5 ecm improves the mileage you have to wonder where the fuel is going with the 05 ecm in control........and in the case of this study is the extra fuel causing the o-heat problem?

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