Rumor and speculation at http://www.dieseltruckresource.com/dev/index.php
as said as the HP/torque ratings go up the milage goes down [img]i/expressions/face-icon-small-sad.gif[/img]

 

I'm not so sure about that. Around here it cost $2.39 for regular unleaded, and $2.79 for diesel. My 1998 Dodge V-10 got 6 mpg when towing a 12,000 lb Weekend Warrior, and my 2002 Dodge CTD got between 6 and 8 mpg towing the same load. My 2005 GMC Durimax gets between 9 and 10 mpg towing a 17,000 lb Dune Chaser. Is 3 mpg worth the extra $4000 initial cost plus the extra $0.40 per gallon fuel cost? The diesel trucks tow better than gas, but cost savings is pretty minimal if you ask me.

DV

 

Thus begins the great debate. First of all you only got 6-8 with the CTD? Wow. That's just really weird.

I'm gonna go weight police on you, but WTF are towing that Dune Chaser with? You need a Class IV or V rig at the minimum.

One thing that a LOT of people don't look at with towing is the frontal area. The larger the frontal area, the less you can tow, or need to account for that. Check your manual. I know there are notes about it in the Ford Towing Guide.

At those fuel consumption rates 3 MPG is 30%. So if we bust out a little math 2.39 x 1.3 = 3.10. Looks good to me still. I figured it out once before, but IIRC, the fuel differential needs to be like in excess of $1/gallon for gas to approach diesel mileage savings. Hopefully that makes sense. Most people just look at a pure dollar amount and don't factor in, or at least REALLY look at the actual fuel bill. Best way is to work out the $/gallon, and MPG on an actual trip to see how it works out.

Here's another big thing, that's controversial. The extra $4K you put into the initial purchase is still there (or mostly there) on the back side when you sell the truck. The same holds true for 4x4. I actually looked at the Blue Book for a 2003 last year and the PSD had an additional $1K over the purchase price differential. IIRC, it was $5K higher, on a $4k purchase adder. The truck didn't loose value as quickly. Every other was the same on the KBB site. Trim, bode, etc. All same conditions as well. Just went and changed the motor.

Yes, maintenance can be higher. Oil changes are better accounted for in gallons, rather than quarts. I think I read once somewhere that the CTD used 18qts of oil.

It really comes back to what the consumer wants and can afford. If everyone looked at practical side of things, we'd all be commuting to work in Toyota Prius, Accord Hu=ybrids, etc. with 3 other people. But that's not that way it works in the real world. If you're towing heavy stuff around, you need some grunt. And grunt takes fuel. And fuel costs money.

For short little stop and go trips around town, diesel probably isn't the best. Of course neither is a big displacement gas motor. The motors like to get warmed up and stay warm. And extended idling is BAD. One, you're getting 0 MPG. And diesels can end up washing down a cylinder.

The truck really needs to be matched to the trailer. There's a big move on now with the Class 8 conversions. These guys are taking 400-600K rigs coming out of fleet work. They are dragging around the biggest of the 5th wheels and still getting 10MPG from big motors. 300HP/900LB/FT+ They can pull a grade without breaking a sweat, let alone a downshift.

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I looked into the bigger ci in the cummins and could find nothing, only available in the bigger rigs. As for fuel, the new emmision standard engines dodge, chevy and ford don't get what they used to, those days are gone. I have the 600 engine and i average 11.5 mpg towing my 11k toy, or my 12k dump trl. The cummins engine takes 12 quarts of oil. Keep in mind that just because they add hp/tq dosen't < fuel. I know several guys with 1 st and 2 nd gen cummins with more than 400 hp rw and get good milage compared to me towing, but thats because of the added injection cycle, retarded timming for the emmisions on the 600 series cummins. In the end i can't complain about milage, my truck weighs 8k all the time and i still get better than my 98 1/2 gmc, which weighed less. Finally, the auto trans are much better than what they used to be, but the key is ditching the stock one and having it re done the way it should be stock to handle the mass weight of towing and added hp/tq, dtt or pdr trans up in canada- I will be having mine done sometime this year.

 

In response to people saying they are not getting favorable fuel milage from a diesel the solution is quite simple.
Stop driving "V" block diesel. The v design eliminates the benifits of the diesel engine entirely.

I have a 12v (before computer engine control) cummins in my dodge. Its a 3500 4x4 dually ext. cab. If I keep my right foot out of the pedal, i routinely see milage over 20 mpg. My truck has some mild mods, putting me barely over the 300/700 range, stock trans.

Cummins design , using a inline 6 lets the cintrifical force of the cranks motion efficiently produce power, by the way spelling of cintrifical is just a guess. Everyone I know, who has a cummins, and adds power agrees, if you can restrain your own habits, which can be tough when your dually can burnout ike a camaro, you will see INCRESED economy.

By the way, my truck weighs just under 7000

 

If your "V" block theory was correct then I would assume the Cummins 600 would be getting better mileage than the Durmax and Powerstroke's. Well I can tell you for a fact they don't.

ALL current diesel motors are seeing reduced mileage for a few reasons, none having to do with being a V8 or I6. The biggest factors affecting mileage are the new emissions that are requiring such things as EGR and catalytic converters on these motors. In addition most of the new diesels including the Cummins 600 are introducing extra fuel injector events on each stroke to quiet down the motors thus again reducing mileage. Just because the cummins is an I6 does not mean it gets any better mileage than the V8 diesels out there. Your old 12V gets killer mileage because it doesn't have to deal with all the emissions and reduced noise measures that are being put on the newer motors, not because it is an I6.

 

Whichever theory you wish to use, My 1996 12v got nearly double the milage of the same year vehicles by chevy and ford.
3rd generation CTD are still routinely seeing milage in access of 18+. Ive invested considerable amounts of time reseraching this. Im not going to replace a truck, with a newer $50,000 truck, only to double my expenses on the vehicle.

Ill be the first to admit, driving habits are hands down the first factor. But after having a 98 F350, manual, for 4 months I got rid of it. My CTD would pull my triple axel eager beaver trailer and get 18 , same setup on the ford, babying it 10 was best I saw.

 

The same displacement engine is in all the cummins powered dodges, and there are other factors that effect the MPG besides ever increasing power.

First is emissions.

In 03 when they switched to common rail injection, power went up, but emissions went down, and it did cost a mpg or two from previous engines. When the 600 came out, emissions went down again with the addition of a cat converter. This required a very late 3rd injection event periodically that only serves to heat up the cat converter to burn off carbon, and the cost is slightly reduced fuel efficiency.

I have heard rumors that future engines might have to increase displacement and reduce compression ratio and combustion temp to meet stricter emissions, but I don't think you will ever see the ISC Cummins in a pickup. It is just too big and heavy.

The other factor that people forget about when they talk about the milage they got with the diesel they used to have is increasing speed. My truck will get around 21, for example, but I'd have to keep it around 60 or so... Get into a 75 speed zone, and milage is around 17.


While we are on the topic, here's a page on the power wars in diesel trucks...



diesel wars

 

I agree as far as the speed is concerened. At 60 im running approximately 1700-1850 rpm, Ill see over 20 mpg all day.
Once i cross onto the high side of 2000 rpm, I start to see a rapid dropoff in economy. Unfortunately with a 3K GSk kit on my truck, I can pull hard to 3000, making higher rpm driving that much more attractive.

But if I had only $5 in my pocket, id definately keep in the right lane, around 55 miles an hour.

In defense of myself, and my post reguarding Inline versus "V" block, be patient, I know I have the paper to prove it around here somewhere. Oh, and Im not sure where DS engineer gets his info from, everyone I know gets just as phenominal milage from there 600. Although, now that I looked, your in california, Last I checked, the emissions out there were downright rediculous. Maybe that accounts for somthing.

 

I've got 37's on my 600 with 4.10's and at 70mph I see right around 17mpg. I can't complain...........