The quote above was taken directly out of the 03 service manual. DC is calling it a catalytic converter.

 

The BEST i ever got stock was 16.5 highway with 285's.In town generally 13.5ish.A few more miles and a few mods i saw 18 m.p.g. on a mixed highway/mountain road trip.Remember too that his rig is a 4x4.The mileage really dumps on the gen3 trucks after 2,000 rpm.I know have heard of very few getting 20 mpg hand calculated.

 

THought the truck in the original thread was an 04.5 with the 600 engine. I've had two 03's and never saw these kind of numbers.

1st one was a six shooter and current one is a 48re, both with HO's.

It's the 600 motor that they have put the cat on and the mileage is in the drain. I've had 4x4's in the past and they generally seem to run about 2 or 3 MPG less than a 2wd

 

"I've had 4x4's in the past and they generally seem to run about 2 or 3 MPG less than a 2wd"

You are seeing 20 plus, and he's seeing 17-18. That seems about right, no? Even so, it seems some people, some trucks, just get better mileage than others. Altitude, attitude, driving style, load...many issues.

I guess I'm not quick to point the finger at the catalyst. Remember that the stock exhaust on an 600 is 4" all the way back. The catalyst was supposed to be designed to be high flow, hence it's large size.

 

Man, I am with you on that. Every truck does do a little different, but driving style, load etc is the real big factor.

 

Your right it was an 04.5 ,thats what i get for answering the business phone while reading/typing on the forum. Must be the H.O.'s are more efficient,not that we dont allready know this. I have the Ca. model with a cat,so i figured it might be pertinent to the discussion.My truck does have a RAMifier module on my truck which gets me over all numbers of about310 h.p. and 544 tq,at the rear wheels.Not so terribly far off the h.o. numbers.Sorry for any misunderstanding.Mark.

 

No problem at all. I thought I had missed something in the translation.

Are all the 04.5 trucks with the HO motor equiped with a cat or only in CA. And, do they still offer a SO motor?

Gary

 

2003 Californail models (235hp) have cat.

As of 2004, there is no Standard/HO. They are all the same rating (2004 is 305, 2004.5 is 325).

 

Not to nitpick but i think the 325-600 is considered a 2004.5

 

My pops just got 16 on his last tank. He has 1100 miles right now.
Do you guys think part of it may be winter blended fuel? I know on mine, I drop 3-4 during the winter. But, needless to say, my dad traded his 02 360 gasser for the heavier truck and opted for the milage to make up the difference in payments. He isn't overly excited right now

What about towing, are you seeing any improvements?
I know it doesn't mean much, but what did your spec sheets say for estimated milage-my dad's didn't have those filled in

 

Hi All.

So far, from data provided on this site 16 mpg seems to be high end of the spectrum, your ad should consider him self lucky in that respect.
Does he experience any other problems like hesitation or clatter?

Regards Jack.

 

No, no hesitation at least when I drove it. And the clatter, all I hear when I slam it is the normal power running through it. It is a bit different because of the 3 events, but it sure doesn't sound like bolts rattling around.

 

A friend of mine took delivery of his new 600 about two weeks ago. Says he got just under 19 to the Canadian gallon which is pretty close to what the computer told him after converting the numbers. He is pretty light on the throttle and I think a fair amount of that was highway under 60 mph.

I do know that these things start getting real thirsty at sustained operation over 2200 engine RPM.

I am not saying that there isn't something wrong with your truck, only that is a bit premature to come to that determination with 600 klicks on the clock.

Casey

 

Man, I'll tell ya 16 mpg really sucks wind. I predict a huge drop in sales. Why would you pay $5K for the option when it gets the same mileage, or very near, as a gasser.

Can't express my disappointment in DC and Cummins.

 

4X4- AUTO- DRW'S get 12 or 13 (2500 mi)