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Old 01-10-2006, 08:42 PM   #1 (permalink)
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Mysterious fuel economy fluctuation

My fuel economy took a nose dive when winter blend fuel arrived. My economy went from a rock-steady 20.0 mpg to 16, 15 and even 14 mpg on my mostly highway, 400 miles per week of commuting.

The onset of poor fuel economy with this year's winter fuel economy was remarkable enough to be a recurring topic here.

Now it is coming back up. [img]/ubbthreads/images/graemlins/shrug.gif[/img]

The mileage, that is . . . and the topic [img]/ubbthreads/images/graemlins/eek.gif[/img]

Two tanks ago I was at 17, and tonight I calculated 18.2

I have added no mods nor made any changes during this period. I still have about 700 miles to go before I reach my next 5000 mile oil change interval.


Has anybody else been experiencing this sort of change?


Does anybody know if the petroleum industry was/is experimenting with their diesel fuel blends? Did they increase the percentage of #1, for instance? Did they cut the #1 with kerosene?


Could it have anything to do with a shortage of some ingredient caused by Katrina?


Is it experimentation with ULSD? [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]
...
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May your road stay clear & dry, may your fuel never gel, and may you never be outsmarted by your idiot lights.


2002 F-250 XLT SC LB 4x4 7.3PSD 6-Sp 3.73 L-S, Snugtop Snuglid Tonneau, 235/85 MC HTRs, <span style="color: red">DPTuner F5</span> AFE Stg II, Turbo LifeSaver, MAP BRV, Autometer Cobalts, Magnaflow 4", WW, TAG, AIH del, CCV, AirDog, In-tank, Harpoon, HPX, ITP fuel sys, LL8 del, 203*, Oilguard & SP Diesel bypass filtration, ART rotors, PFC pads, Heater Core Ctl Valve, Bilsteins, Velvet Ride Shackles, South Bend Clutch, <span style="color: green">21.27 mpg</span>

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Old 01-10-2006, 09:10 PM   #2 (permalink)
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Re: Mysterious fuel economy fluctuation

During the Katrina shortage, the EPA lowered restrictions on sulfer content and batch processing (different specs for different parts of the country) in order to stimulate fuel production. The companies that bought this oil had until January to get it out of thier tanks. My uncle in KY was filling up last month and looked down and was pumping off-road fuel, this fuel was coming from Shell. Oil companies use futures as a common part of thier business. Meaning they Sell High, Buy Low. I'm sure that some companies stocked up on the cheaper, more-abundant fuel while they could and then waited as long as they could to sell it, depending on what the going price was/is.

The sudden drop in fuel mileage could be easily attributed to the last of one of the crappy batches of fuel.
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Old 01-11-2006, 10:35 AM   #3 (permalink)
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Re: Mysterious fuel economy fluctuation

Yes, mine dropped after Katrina, and several friends with diesels noted the same thing. Fuel here seemed particuraly bad. Most went with Cetane boosters.
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Old 01-11-2006, 12:54 PM   #4 (permalink)
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Re: Mysterious fuel economy fluctuation

I've seen similar fluctuations this winter.

My worst mileage was with a tank of 60% biodiesel and 40% BP/Amoco standard diesel (not altogether unexpected due to the lower BTU content of biodiesel). My best mileage was with a tank of BP/Amoco Premier Diesel.

My area of the country has seen some pretty wide fluctuations in temperature this winter and I'm sure that accounts for a difference in mileage too.

My own personal experiment is to going to be to "standardize" on the best mileage fuel for a few fills and see if things stabilize.
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Old 01-12-2006, 08:38 AM   #5 (permalink)
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Re: Mysterious fuel economy fluctuation

Do you have a locking cap for your fuel tank? Sometimes that can help your mileage tremendously.
Hopefully what I'm insinuating is not the case here as you describe your mileage going down and gradually coming back up. If somebody was helping himself to your fuel then your miles per tank would rise and fall suddenly. ..........JIM
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Old 01-12-2006, 03:13 PM   #6 (permalink)
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Re: Mysterious fuel economy fluctuation

I have been amazed since owning a diesel, how much the mileage fluctuates. 17.5 summer is about average. Winter about 15 unless it get really cold (zero to +15F) it will drop to as low as 12 and never above 13.5 in that temperature. I wonder if a winter blanket on the grill would help.???
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Old 01-12-2006, 06:49 PM   #7 (permalink)
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Re: Mysterious fuel economy fluctuation

My MPG also wanders around a bit in the winter. Fuel variation may play a part but it seems to happen every winter.

I think driving conditions affect me a lot. To get big MPG, you need to drive smoothly and that isn't always possible in the winter. Goofy drivers, slick roads and poor visibility conspire to make your speed control less than what it should be.
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Old 02-03-2006, 05:44 PM   #8 (permalink)
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Re: Mysterious fuel economy fluctuation

[ QUOTE ]
Two tanks ago I was at 17, and tonight I calculated 18.2

[/ QUOTE ]

Update: last week: 18.0
and, just in this evening: 18.7 . ! ! ! ! [img]/ubbthreads/images/graemlins/eek.gif[/img]

It's the middle of winter [img]/ubbthreads/images/graemlins/tongue.gif[/img] That means winter fuel, right? [img]/ubbthreads/images/graemlins/shrug.gif[/img]

I've got my Mastercraft 265 size Courser C/T mud and snow tires on it. [img]/ubbthreads/images/graemlins/shrug.gif[/img]

It's 6000 miles since the last oil change. [img]/ubbthreads/images/graemlins/shrug.gif[/img] (I'm changing it tomorrow. [img]/ubbthreads/images/graemlins/wink.gif[/img] )

I usually get 14, 15 or 16 in the winter.

18.7 What's up with that? [img]/ubbthreads/images/graemlins/shrug.gif[/img] [img]/ubbthreads/images/graemlins/shrug.gif[/img] [img]/ubbthreads/images/graemlins/shrug.gif[/img]

We need a smiley that's squiggle-eyed with confusion and scratching his head. [img]/ubbthreads/images/graemlins/crazy.gif[/img]
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"Nothing in life is so exhilarating as to be shot at without result." - Sir Winston Churchill

May your road stay clear & dry, may your fuel never gel, and may you never be outsmarted by your idiot lights.


2002 F-250 XLT SC LB 4x4 7.3PSD 6-Sp 3.73 L-S, Snugtop Snuglid Tonneau, 235/85 MC HTRs, <span style="color: red">DPTuner F5</span> AFE Stg II, Turbo LifeSaver, MAP BRV, Autometer Cobalts, Magnaflow 4", WW, TAG, AIH del, CCV, AirDog, In-tank, Harpoon, HPX, ITP fuel sys, LL8 del, 203*, Oilguard & SP Diesel bypass filtration, ART rotors, PFC pads, Heater Core Ctl Valve, Bilsteins, Velvet Ride Shackles, South Bend Clutch, <span style="color: green">21.27 mpg</span>

2004 <span style="color: red">E</span>-350
XLT Wagon 6.0PSD 3.55 L-S TDM EZ-Entry 11 pass., AIC, custom MBRP 4" w/dual Aeroturbines, Airdog, harpoon, Overhead Cobalts
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Old 02-03-2006, 06:14 PM   #9 (permalink)
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Re: Mysterious fuel economy fluctuation

It's no myth. Over Christmas my family and I drove our 1966 GMC 4107 bus from CO to CA to visit family. I filled up in CO before I left, and got [censored] mileage from here to Arizona, where I topped off the tank. Got great mileage from there on out. At the best of times, she gets 10-11 MPG, with the crappy CO winter fuel, if I got 6 I was lucky.
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