Fuel Mileage

   / Fuel Mileage #41  
FlaDon said:
High speed cameras have been used to film gasoline in an engine from the point of combustion and proven that it is not an explosion. An explosion is an uncontrolled burning of fuel while an engine is a very controlled burning of the fuel. It is a buildup of pressure along a rapidly moving flame fronts that are controlled by such things as piston domes and combustion chamber designs in the heads. Gas tanks explode because the pressure and liquid is contained until rupture and the exposed to air in a large volume of heated vapors. The term for that tank explosion is a BLEVE. Boiling Liquid Expanding Vapour Explosion It is the rapid expansion of the liquid to a vapor that causes it. The same thing as happens in a boiler explosion when water turns to steam.
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Do you have any of that video footage?, I'd be interested to see it.
 
   / Fuel Mileage #42  
Just returned from a Ohio to Florida and back trip. With a 2008 LMM 2500HD Crew Cab chevy. My mileage seems to vary by 1-2 m.p.g. based on where I filled up last. My mileage seemed to drop from around 20 to 18 on the tank crossing West Virginia. The next tank was closer to the first, but there were less hills. I usually do a quick mental calculation based on miles driven a gallons added, and never look at the computer calculation.

The truck has just under 30,000 miles on it.

I do feel that the winter fuels seemed to affect my mileage last year also.
 
   / Fuel Mileage #43  
As explained by Fladon regarding a quote by WH401,
Gasoline combustion in an engine does not explode. If it exploded that would be called detonation which can destroy a gasoline powered engine very fast. Gasoline combustion, subject to the octane, the compression ratio, ignition timing, and other variables is a controlled event. When I flew heavy multi-engined aircraft we used heavily leaded aromatic aviation fuel. A common radial engine that I flew extensively was the 18 cylinder Pratt and Whitney R-2800 Double Wasp Engine that we used 115/145 octane aviation fuel and to prevent detonation at high power levels (2,500 HP) during take-off we used water injection (ADI) to control the combustion temperatures. In gasoline powered engines such as found in automobiles, motorcycles, etc when you lug an engine and hear pinging that is a mild form of detonation that can, over time, destroy an engine.
Jim
 
   / Fuel Mileage #44  
   / Fuel Mileage #45  
jlrsn said:
As explained by Fladon regarding a quote by WH401,
Gasoline combustion in an engine does not explode. If it exploded that would be called detonation which can destroy a gasoline powered engine very fast. Gasoline combustion, subject to the octane, the compression ratio, ignition timing, and other variables is a controlled event. When I flew heavy multi-engined aircraft we used heavily leaded aromatic aviation fuel. A common radial engine that I flew extensively was the 18 cylinder Pratt and Whitney R-2800 Double Wasp Engine that we used 115/145 octane aviation fuel and to prevent detonation at high power levels (2,500 HP) during take-off we used water injection (ADI) to control the combustion temperatures. In gasoline powered engines such as found in automobiles, motorcycles, etc when you lug an engine and hear pinging that is a mild form of detonation that can, over time, destroy an engine.
Jim
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Not only water injection but also alcohol. Very common on fighters such as the Me-109 and FW-190. Prevented detonation and increased power. Were you flying a DC-6?
 
   / Fuel Mileage #46  
jcmseven said:
Dodge Man,

I think you make a solid point here. I tow to keep up with traffic, unless I am towing something really heavy. The interstate where I live is mostly 65-70 mph speed (mostly 70). If one drives 70, even in the right lane, people swing in front of the driver, run up on the driver, etc. To keep up with traffic flow, it becomes essential that one go around 70-75, which is generally where I tow. The truck has no trouble pulling at that speed and it generally tach's around 1800-1900 at that speed. Thinking that might be the "sweet spot" for towing, that is where I have kept the truck, but clearly it does not seem to like that speed. Without your having seen my trailer I can tell you it is an aerodynamic brick and likely has some role in the reduced mileage. That still to me, though, does not fully explain why my mileage dropped as is did. I was getting around 2-3 mpg better pulling the same load at the same speeds about 3 months ago. The truck runs great. What gives?? Is it truly more efficient to tow in tow/haul mode or in regular overdrive in this case?? Also, to me a load of this weight is a "light" load for this truck. Am I wrong here??

John M
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I have a 2500 DMax and have a very heavy Holiday Rambler fifth wheel, and have also pulled several different trailers loaded to varying degrees, tractors, hay, etc. My fuel mileage also varies at times, and I think the winter blend hurts your fuel mileage, and also I think the fuel pumps are off....you don't pump the number of gallons you think you do, yea it's suppose to be illegal but I'm certain it happens, and that messes up your mileage calculations.

Yes speed kills mileage. My sweet spot is 62-65...but I more consistently pull at 70mph.

I tach 2000 at 70 on speedometer, corrected is 72 with my 265/75/16 tires. What size tires do you have on your truck? Your rpms don't sync with mine.
 
   / Fuel Mileage #47  
jcummins said:
I have a 2500 DMax and have a very heavy Holiday Rambler fifth wheel, and have also pulled several different trailers loaded to varying degrees, tractors, hay, etc. My fuel mileage also varies at times, and I think the winter blend hurts your fuel mileage, and also I think the fuel pumps are off....you don't pump the number of gallons you think you do, yea it's suppose to be illegal but I'm certain it happens, and that messes up your mileage calculations.

Yes speed kills mileage. My sweet spot is 62-65...but I more consistently pull at 70mph.

I tach 2000 at 70 on speedometer, corrected is 72 with my 265/75/16 tires. What size tires do you have on your truck? Your rpms don't sync with mine.
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Remember he has a 6 speed ally while all the pre 06's were 5 speed. Also rear axle ration will vary that. I think now all they offer is a 3.73 but at one time the 4.10 was available in the SRW trucks.

Chris
 
   / Fuel Mileage #48  
Diamondpilot said:
Remember he has a 6 speed ally while all the pre 06's were 5 speed. Also rear axle ration will vary that. I think now all they offer is a 3.73 but at one time the 4.10 was available in the SRW trucks.

Chris
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I have a GMC 03 Duramax 3500 with the 3.73 rear end. I have always been a little disapointed with my non towing mileage. I know guys with the same engine and transmission in 2500 series trucks that get 19-22 mpg. I rarely drive my truck without towing something but when I do it has never got more than 18 MPG. On the other hand I have hauled 8 horses to Mount hope Ohio and got 13.5 MPG running at the posted speed limit. I recently had a tank full of fuel used pulling a 10,000# excavator on a 3,000# trailer and followed it up with towing a 8,000# load of concrete block and morter. Almoast no non towing miles on that tank and I got 16 MPG. So I suppose I am happy with my towing mileage, but I use my Chick magnet Ford Escort station wagon when I don't need to move real heavy stuff.:D:D:D:D

I do get around 13 miles per gallon when towing my fifth wheel camper that weighs about 9,000# at 65 miles per hour. It will drop to 11 if I drive 70+. I had to remount my springs from the bottom of the axel to the top of the axel on my trailer because the truck sits so high. I am pretty sure that the additional 6 inches of height costs me a mile or two per gallon based on past experience. I have no idea why the truck builders think they have to have a tail gate that is four and a half feet off the ground:confused:

I suppose it is a style thing, big tall manley truck, but it sucks when you have to put something in there. Try throwing 80 pound bags of morter that high into the air and beyond the tailgate. By the time you get to the tenth one you will wish for a nice low half ton. It is a stupid design. Give me a 1 ton low rider any day, I won't have to raise my trailer or break my back loading it. (I don't care about the bad *** looks I just want to haul heavy stuff without breaking my back getting it up there) :D:D:D:D:D
 
   / Fuel Mileage #49  
You think the GM trucks sit high try the Fords and Dodges. I have had all 3 and my 3500 GM Dmax sat the lowest of the 3. My current F-350 sits up pretty good but I like the looks and styling.

Chris
 
   / Fuel Mileage #50  
Is it just me or did everyone else see a drop in their mileage with the new ultra-low sulfur diesel fuel?
 
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