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Old 11-04-2014, 01:12 PM   #15
Builder of Diesel Jeeps
westernjeep401's Avatar
2014 28' International
Sedona , Arizona
Join Date: Sep 2014
Posts: 214

Originally Posted by Msmoto View Post
My question is this: For those who are pulling with diesel engines, has anyone else noticed a decrease in fuel mileage over the past few years?
Of course, the wind factor may be entirely to blame, and the fact I am 500 lbs heavier may be the problem. but I was curious about others experience.

I am head east in a week, then back south east so I will reassess the overall fuel mileage once the trip is complete. I was just disappointed to be pulling at about 62 - 64 mph and have what I consider to be poor fuel mileage.

Thanks for any thoughts on this issue.
Hi Msmoto,

I do not currently pull using a diesel power train such as yours, I am a diesel tech and fleet manager that uses the Cummins B, C, M, and X, among others.

Yes there are many variables that are just too subjective to distill a definitive answer with some trends to graph. Very generally, AIR FIRE FUEL.

AIR: reference to condition and ability of the base engine to pump and power.
FIRE: reference to combustion
FUEL: reference to agent used to create the flame event

They are interdependent; the greater truck is an interdependent machine with the power train as it's heart.

Let's explore a scenario: a diesel power train such as yours averages x over y time fuel usage to provide you a fairly steady, normal level of performance. You're satisfied until fuel economy starts to suffer, and it's of note enough to discuss. As a tech, the systems pre-checks such as tire pressure and condition, axle alignment, service/parking brakes dragging, even just a little due to debris build-up, clean and clear engine air filtration, clean and clear cooling package fins, engine coolant condition, coolant thermostat cycle time, DPF condition (logs of cook cycles, which require fuel, like a self-cleaning oven), fuel system condition and fuel quality, any aftermarket modifications such as lifts, tires, software mods, unnecessary cargo name a few things you can do yourself.

A customer with a 6.0 years ago had a similar issue. No codes, steam, burping, ran great. It ended up being a twinkie wrapper partially blocking the big Donaldson air filter intake. Another had a 6.5 Detroit turbo diesel that was experiencing higher than average fuel consumption, with ended-up being dragging service brakes. Finally, a late Ford SD 7.3 owner was distraught that his puller had descended into the 5-6 mpg range within a 4 week period. The base engine had very high crankcase pressures, and was near the end of its service life. It kind-of was a learned compensation on his end...more and more throttle, then a spate of diesel fuel price spikes. It still pulled well (by his standards, but once in a newer unit on the lot he understood how much he had been flogging a worn-out engine. Likely not your problem, however a sensitive, observant operator notes fuel consumption, which is you.

Hope this provides some mental carrots.

14 Serenity 28'
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Old 11-04-2014, 02:30 PM   #16
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Fort Worth , Texas
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Excellent post!!

I forgot about the hoses to the CAC

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1990 35' Silver Streak Sterling; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 12-cpm solo, 19-cpm towing (fuel)
Sold: Silver Streak Model 3411
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Old 11-04-2014, 03:15 PM   #17
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2014 28' International
Blacksburg , Virginia
Join Date: May 2014
Posts: 257

Once you get out of the mountains, I can roll 14 mpg down I-77 headed south with the AS, consistently. Its always less coming back home. It will be less here at the end of the week, I had to put the BFG's back on. They do not roll as easy as my old Michelin's. I finally wore them out. Well more specifically they are ten years old and have some substantial cracks in them, so I put the BFG's back on.
Next time Costco has the rebate on the Michelins I plan to get a set.
Haven't really noticed a decrease in fuel mileage.
I try to do everything 'Slowmover' recommended, except I don't have th eheater for the coolent. I keep a trickle charger on the batteries and use the Hastings air filter, Fleetguard fuel filters. I like the Rotella synthetic oil, its very good.
I have the deep transmission pan and aluminum PML rear differential cover that adds extra oil (synthetic 75w-90), recommended in the AAM axles.
Just changed the coolant in preparation for this two week trip coming up. It was time. I have a special brush for the inter-cooler fins.
Have been adding the Power Service cetane boost and 2 cycle oil every now and then since the EPA removed all the sulfer. Diesel fuel has come down a bit in price.
'Big-D' has been steady on fuel mileage. It does great when not towing, if you can keep your foot out of it
Have a good one !

Ra, Chelle & Natasha
For my next trick, I will use my new Airstream & Dodge Ram 2500 CTD to make this pile of money disappear.
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