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Old 11-04-2014, 01:12 PM   #15
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westernjeep401's Avatar
2014 28' International
Marietta , Georgia
Join Date: Sep 2014
Posts: 206

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 Serentiy 28' "Built by British Leyland"
74 IH 100 Travelall Custom "Sal"
75 IH 200 Pickup 4x4 "Hal"

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Old 11-04-2014, 02:30 PM   #16
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Corpus Christi , 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. 10-cpm solo, 18-cpm towing
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: 182

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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