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Old 03-10-2008, 05:02 PM   #71
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Still more efficient

Quote:
Originally Posted by azflycaster
The numbers you use need to be adjusted. It takes about 20% more oil to produce diesel then it does gasoline. Also what abouit MPG when not towing? Since I only tow one weekend a month on average and my non towing MPG is very good (18+), I use less oil with my gasser then I would with a diesel. If I was full timing, it would be different.
Even if I bump my numbers for diesel up by 20% I'm still burning 50 gallons less diesel than I would be gasoline every 1000 miles. That's my situation, which is a little more extreme with my 7 mpg figure. In my case diesel is a much more efficient use of fuel.

I use the Excursion for 90% towing. I commute in a more fuel efficient sedan or I'd be broke. However, I get between 21 and 22 mpg highway when not towing with the Excursion. That's pretty awesome for an 8,000 pound pig.

The only thing that graph shows is that 10 gallons of that 42 gallon drum goes toward making diesel and 19.6 gallons goes toward making gasoline. It does NOT mean that it takes 42 gallons of crude to make 10 gallons of diesel like sky might be implying.
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Old 03-10-2008, 05:18 PM   #72
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I am implying just that

Quote:
Originally Posted by TinLoaf
blah blah blah

The only thing that graph shows is that 10 gallons of that 42 gallon drum goes toward making diesel and 19.6 gallons goes toward making gasoline. It does NOT mean that it takes 42 gallons of crude to make 10 gallons of diesel like sky might be implying.
The problem with crude oil is that it contains hundreds of different types of hydrocarbons all mixed together. You have to separate the different types of hydrocarbons to have anything useful. Fortunately there is an easy way to separate things, and this is what oil refining is all about.

From what I am reading, 10 gallons of a 42 gallon barrel contain the type of hydrocarbons used to make diesel. So, yes I am implying that you can only get 10 gallons of diesel out of 42 gallon of crude. But, the other 32 gallons obviously don't go to waste.

But, I have been wrong before

Anyway TinLoaf, I agree with you also. I wouldn't trade my diesel truck for the world!
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Old 03-11-2008, 03:32 PM   #73
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For whatever it's worth, we towed over 5,000 miles from lower Alabama to Maine, and returned last summer. We have a 2,000 30' Excella, and a 2003 Donge/Cummins - 6 speed manual, 3:73 rear end....2 wheel drive - of course.
I averages 15.0 mpg at speeds of 55 to 60 mph.
I carry an extra fuel tank (115 gallons) to give me a total capacity of 155 gallons..(145 usable). It gives me the option to shop price for fuel, as we all know, it can vary as much as 0.25/gallon..
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Old 03-11-2008, 06:31 PM   #74
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Quote:
Originally Posted by Larry C
For whatever it's worth, we towed over 5,000 miles from lower Alabama to Maine, and returned last summer. We have a 2,000 30' Excella, and a 2003 Donge/Cummins - 6 speed manual, 3:73 rear end....2 wheel drive - of course.
I averages 15.0 mpg at speeds of 55 to 60 mph.
I carry an extra fuel tank (115 gallons) to give me a total capacity of 155 gallons..(145 usable). It gives me the option to shop price for fuel, as we all know, it can vary as much as 0.25/gallon..
Larry C

Pretty much the same rig as mine. What does your combination weigh? Our numbers are otherwise similar:

Tow at 63 mph
15+ mpg on Interstate
13+ mpg on secondary highways
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Old 03-11-2008, 08:35 PM   #75
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Fuel Milage

My 2006 Hummer H1 Alpha with the Duramax engine and Allison transmission combo with 19,000 miles gets me approximately 20 MPG highway and 17 MPG in city. Towing my 2006 22-0 CCD gets me approximately 15 to 16 MPG highway. Highway speed defined as 55 to 60 with rpm at no greater than 2000. So far, the Duramax/Allison combo in the H1 has resulted in reasonable fuel milage. Hopefully it will improve as the engine gets completely broken in.
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Old 03-12-2008, 07:29 AM   #76
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Quote:
Originally Posted by MrAgent007
My 2006 Hummer H1 Alpha with the Duramax engine and Allison transmission combo with 19,000 miles gets me approximately 20 MPG highway and 17 MPG in city. Towing my 2006 22-0 CCD gets me approximately 15 to 16 MPG highway. Highway speed defined as 55 to 60 with rpm at no greater than 2000. So far, the Duramax/Allison combo in the H1 has resulted in reasonable fuel milage. Hopefully it will improve as the engine gets completely broken in.
Cool, that is pretty much in-line with what other D/A drivers (and for that matter pretty much all the diesel Folks) are getting for mpg.
I didn't know they were putting the D/A in the Hummer now?! Very cool setup.

It would seem, on average, that most Folks towing with small block ½ tons are getting 11-12 mpg (believable) or worse if overburdened, while most diesel Folk’s are getting 14-15 mpg (also believable) towing. Occasionally someone claims something way outside these averages, but there are bound to be anomalies and fliers in any statistical sampling. (It is kind of funny some of the outrageous responses people post that are way outside the bell curve. I guess that's why reading these forum is so much fun. Don't believe everything you read...)
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Old 03-12-2008, 07:55 AM   #77
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Quote:
Originally Posted by REDNAX
Pretty much the same rig as mine. What does your combination weigh? Our numbers are otherwise similar:

Tow at 63 mph
15+ mpg on Interstate
13+ mpg on secondary highways
Our weights are a bit different, because of the 115 gallons of extra fuel in the aux tank...mine will be around
Truck weighs around 8,000.
AS (depending on how it's loaded) around 8,000.
This is the second Dodge/Cummins, and we love it! Especially when in mountains, I equipped this one with the exhaust brake, and I've never felt safer when goiing downhill.
Take care
Larry
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Old 03-17-2008, 08:50 AM   #78
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Some observations from a 700 mile ski trip this past weekend. Not really scientific, but real world data anyway;
Performed a little experiment on Rt 89 through mountains of Vermont and NH (at least we call them mountains here in New England!). This is a rolling highway, usually light traffic up North which allows you to set the cruise, kick back, and let it roll. Total payload (5 passengers, ski/snowboard gear) estimated at 1300-1400 lbs plus full tank of diesel. Each leg of the test was done for ½ hour, truck has the 6spd Allison, cruise control was on, tranny in “D,” mpg as reported by DIC.
On open road when not towing, I typically set the cruise at either 69 mph or 73 mph if there is not traffic. After paying ~4.00/gallon for diesel I was very determined to find out the point of peak economy for my truck.

65 mph
1600 RPM. Average fuel economy 17.6 mpg. This was very surprising and disappointing.

69 mph
1750 RPM. Average fuel economy 22.2 mpg. Wow, this was great!

73 mph
1900 RPM. Average fuel economy 22.4 mpg. This also was very surprising and better still.

I did not try any other speeds as these are typical for my driving style and we were starting to get into more traffic by this time.
The remainder of the trip yielded 20.0 mpg through Boston traffic. Traffic was flowing at about 70 mph (not bumper2bumper) but had normal brake tapping and slow downs.
Overall mpg for the trip; highway, back roads in the mountains, and Boston traffic yielded 20.2 mpg. I do not have the power curves for this engine/tranny but will look them up when I get a chance. If anyone else has them available please post, this might help explain the poor mpg at 65 mph.
This was for me, one of the most in-depth studies of mpg for a typical non-towing weekend. The recent spikes in fuel costs are what motivated me to take a close look at how we are doing with fuel. In summary, I was pleased with the efficiency of the ¾ ton diesel. I never got these kinds of returns driving any gasser (I have owned 3 ½ ton small block gas pickups and 2 ½ ton small block gas Suburbans). For those that drive ½ tons, let’s hope the diesels start hitting the market soon. It has been my experience, that diesel engine fuel efficiency is for real. Imagine what the diesel hybrids will do?

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Old 03-17-2008, 09:39 AM   #79
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OK-found one. It would appear that fuel consumption was greater at peak torque. This would make sense.

Interesting.

Bill
Attached Files
File Type: pdf 2006_66L_LBZ_Sierra power curve.pdf (17.3 KB, 45 views)
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Old 03-17-2008, 09:50 AM   #80
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Just the gas mileage...

Don't know what a diesel engine might show, but for what it's worth, our longest sustained test of gas mileage produced a 13.4 mpg average covering nearly 9,000 miles from California, across the Sierras and Rockies, thru the plains, across part of Canada, over the very steep grades of upstate New York and Massachusetts, back down thru the steep grades of Pennsylvania and Maryland, back thru the midwest and south to Texas, across the high deserts, and eventually to the new home in Arizona. A lot of meandering around along the way, too.

All this with a 5.7 liter gasser pulling the heaviest load we have ever hauled because we had sold our home and expected to live in the trailer for 6-8 months. I wouldn't be surprised to learn that we were carrying over 7,000 pounds for much of the trip.

In all, we are very happy with this gas mileage and the fact that the Durango burns regular, unleaded gasoline...the cheapest grade except in Nebraska and Iowa where we burned the mid-grade with more ethanol and a cheaper price.
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Old 03-17-2008, 12:15 PM   #81
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Quote:
Originally Posted by BillTex
OK-found one. It would appear that fuel consumption was greater at peak torque. This would make sense.

Interesting.

Bill
Bill, maybe I am miss understanding you, but the best mpg you can get in a vacuum is when the engine is at peak torque. Add in air resistance, and it is a little below peak torque. On a DuraMax 6.6 with Allison, thats about 1500 - 1600 rpm or 55 to 60 mph.

Sorry, but I don't believe your real world data . You sure your DIC is accurate and the terrain was the same each test?

Dale
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Old 03-17-2008, 12:36 PM   #82
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Quote:
Originally Posted by Sky
Bill, maybe I am miss understanding you, but the best mpg you can get in a vacuum is when the engine is at peak torque. Add in air resistance, and it is a little below peak torque. On a DuraMax 6.6 with Allison, thats about 1500 - 1600 rpm or 55 to 60 mph.

Sorry, but I don't believe your real world data . You sure your DIC is accurate and the terrain was the same each test?

Dale
Dale, I am not sure you will get peak efficiency at peak power (tq). You could also assume peak output (tq) would require maximum fuel consumption. If I had more time I could have tried the test on either side of 1600 rpm (max tq output for this Duramax).
But as you also noted, my peak efficiency was "a little below peak torque". So what's not to believe?

The DIC is accurate, I have verified by calculation many times.

One big variable (I did say this wasn't very scientific-just some observations from this past weekend) is elevation, as you noted. The tests were all done on the same stretch of highway, in Vermont and NH, but I did not have an altimeter with me so could not measure total elevation (gain/loss) for each 1/2 hour leg of the test. Anecdotal observations were that elevation gain/loss were about the same (i.e. I did not go from the mountains to the prairies durring the test).

I was stumped by the numbers also, if I had more time (traffic patterns began to change and no longer would make for a "fair" comparison.) I would have repeated the 65 mph leg.


Do you have any data on peak efficiency of the Duramax?

Thanks, Bill
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Old 03-17-2008, 02:42 PM   #83
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Hi Bill,
I swear the "Brake Specific Fuel Consumption" link once worked on this page, but it no longer works for me. Maybe you will have better luck. Here it is.
TheDieselPage.com Feature Articles

Here is another article that alludes to best mpg @ peak torque. Hit ctrl-F and search for peak.
Diesel Economics and Fuel Mileage, TheDieselPage.com

Here is another article
Technology

I did a Goggle search on this subject about 1 1/2 years ago, and it seemed to find alot more information on the subject then it does today. I performed a test like your's this past fall while driving through western Indiana and Illinois on a calm day. My 2006 Silverado 6.6 DuraMax with 2WD and 3.78 rear end obtained best mpg between 50 and 60 MPH.
If you can consistently get 22MPG at 73MPH, then You Da Man!! I'm jealous!


Take care
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Old 03-17-2008, 03:44 PM   #84
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Quote:
Originally Posted by Sky
Hi Bill,
I swear the "Brake Specific Fuel Consumption" link once worked on this page, but it no longer works for me. Maybe you will have better luck. Here it is.
TheDieselPage.com Feature Articles

Here is another article that alludes to best mpg @ peak torque. Hit ctrl-F and search for peak.
Diesel Economics and Fuel Mileage, TheDieselPage.com

Here is another article
Technology

I did a Goggle search on this subject about 1 1/2 years ago, and it seemed to find alot more information on the subject then it does today. I performed a test like your's this past fall while driving through western Indiana and Illinois on a calm day. My 2006 Silverado 6.6 DuraMax with 2WD and 3.78 rear end obtained best mpg between 50 and 60 MPH.
If you can consistently get 22MPG at 73MPH, then You Da Man!! I'm jealous!


Take care
Dale
Dale, I will take a read at those tonight, but I was running a little under peak torque (could this be said for either side of the RPM curve?) Not sure, as of course there would be diminishing returns due to friction...
I ran out of good traffic conditions before I could try any further testing and I am not patient enough to run slower than 65, although as the cost of fuel rises, so will my search for increased mpg!
I have consistently returned 21 mpg on the highway for 2 years now. I am getting more miles on the truck so maybe it is bumping up further still (17k miles now).
I don't use this truck daily, it only gets out for tow duty or advnture trips (skiing, yaking, etc). But I will continue experimenting next time out.

I think you have 3:73's on your truck also...

All in all I am very pleased with the diesel, as noted I never got this kind of mpg with a gasser.
Thanx for the linx
Bill
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