03CumminZ4X4

Thanks to all of you!

After reading all the comments about the new 600 engine and the questionable fuel mileage I wanted to drive one for myself and see. My dealer was trying to trade me out of my 03 HO 4x4 auto for a 04.5 6spd 2wd dually with the 600. He dealer transfered the truck and called me to come drive it. I agreed to try it but told him of all the bad fuel mileage press the new cat/600 was getting and that I would not go through with the trade until after an extended test drive. He agreed to let me check it out. The dealership is located next to I 75 and so I took the new truck out for a spin. Bad news!! with the cruise set at 68 to 70 in 6th running it here for 50 miles or so and resetting the overhead several times The best she would do is 13.2 . My 03 auto 4x4 back at the lot left the dealership new getting over 17 on the overhead the first day and at 20k had only gotten better. I pulled back in and told him what had happened with the mileage and that I would not be interested in a trade for that truck. He looked like I had kicked him in the gut for a second and I told him that is what we agreed upon. He then said you are right and that he didnt blame me. I then happened to think that I would try to locate a truck like mine except in a 3500 303/555 6spd. Found the exact truck in Cambellsville Ky. The 305 trucks are getting harder to come by with every passing day. My dealer called and bought the truck from the dealer and sent a driver to pick it up that day. By 11pm that same evening I go back to the drivers house and pick up my new 04 305/555 3500 srw sb 6 spd slt loaded with everything pretty much except leather! on the way home with 250 miles on it the overhead went up to as high as 21.4mpg. So glad I read you guys post about the mileage and the 600. Oh yeah why did I ever want an auto! Love that 6 spd!! The 600 did not feel any stronger in my opinion than the 555 engine and no KITTY. Sorry so long! Thanks again!

dwhite

I am happy to hear how fortunate you were. It is posts like yours that make all my comments about the poor mileage with my 600 worthwhile.

Maccandy

My first 300 mile trip on my 04.5 I got 18.5 mpg. I have only 500 miles on it now so I hope it will even get better.

thames1948

That is good that someone else didn't get stuck with a fuel guzzler 600. Sure wish I would have known. I believe if DC don't do something about this, there will be alot more like you. In the meantime untill then I will tell it like it is except to people with the fxxd and cxxxy because they look at me funny when I tell them 13 mpg on a 40,000 dollar truck.

wyosteve

It doesn't seem like one should generalize about the 600 fuel mileage. I just hand calc. my first tank and come up with 16.47. My 01 would only get 16.5 to 18 w/ my driving habits.

03CumminZ4X4

Wyosteve

Your mileage sounds reasonable. The 600 I drove sucked fuel and couldnt tell seat of pants difference in power between the two. It was an apples to apples comparison to the 555. The 555 won hands down. Sounds like your truck is reasonable at 16 plus with the 600 but I was not going to chance it. I have to listen to the overhead computer, the 03 I traded in on my current truck was extremely close to hand calculations always and there aint no way I can ignore 13.2 on the overhead in a 2wd 6spd 04.5. Oh yea filled up today and hand calculated mileage 21.2 mpg with less than 800 miles on it . That makes a heck of a difference in $'s for fuel over time. Good luck with your ride! Sounds like your one of the lucky ones to break 16mpg. Hope it gets better for all 600 and 555's alike. With fuel prices going sky high we need all the help we can get!

spudman

first of all if you keep resetting the computer if its like mine the milage will look bad leave it alone and drive the truck. If you do that look at it 30-40 miles later mine is nearly always 19-22mpg now. I love my 600 and I can't be the only one. and from what I read the 555 is only 17-18 mpg thats pretty **** bad considering the old 460 gets 22-24mpg

03CumminZ4X4

Spudman

This is my fifth CTD and third CTD truck with the overhead computer. They have all three been very close to hand calculations for me. I think I am qualified to operate it by now! I drove the 600 on the interstate for an extended period and reset the mileage three times at 68 to 70 on cruise each time running 20 + miles before the next reset. Same stretch of road, same speeds one 600 2wd and my new 555 4x4 both 6spds w/373's. My comparison is apples to apples! The 555 is better by far with the fuel mileage! Period!

Vaughn MacKenzie

My truck is pretty much the best MPG configuration, and my first tank last year was less than 16 (about 15.5). It was mostly running around town and breaking it in, about 1/3 of it highway.

Since then I average 17 in town unless it's winter fuel and 21 on the highway running low 70s. Did 23 once running 65. Steady 78-80mph gets me about 19.5. I have 27,000 miles now.

Vaughn

Jonny Two Guns

I've said it many times in many different threads. You must look carefully at each person's truck's configuration. YOU JUST CAN'T COMPARE AN AUTOMATIC TO A STICK! The guys with Auto's get a few less miles per gallon than the Sticks.

Also driving habits mean alot. I rarely accelerate my truck over the 2k point. Why cause I like the 15-16 in town and the 21-22 on the Freeway. That's what the computer says. Now, hand calculated is almost always 18ish per gallon. That's an average and I'm very happy. If I leave the computer alone for a few tanks guess what it says 17.9 I've got to conclude the computer is pretty accurate.

Oh, and just my two cents worth. I bought a 3500 Diesel for my daily commuter. Why? Cause I'm a fat, fuel guzzeling american! I can afford it. I wanted it and although I'm a tight bastard with my money. I've got to figure a big truck like mine is going to eat fuel. So I live with what I paid for.

dwhite

But if you had gotten a 600 with your configuration...you would be getting 13 to 14 just like me...I keep it always below 2000 and mostly @1700 to 1800 and still only get this kind of mpg. I used to drive 80mph on the highway...now I drive 60 to 65mph and get my doors blown off....oh but I got 25 extra horses.........

thames1948

I never hot rod mine and drive it very easy. I have never ever seen past 13.2 even with driving at 65 down the freeway for 45 minutes. I am taking it to the same dealer in the morning that the service manager told me when I meant him and told hjm I bought a diesel said, oh, you will like the milage. I will see if they can figure it out.