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ummm 31-35 is not that far off at those speeds when in such hilly highways... when i went to lords town through Tennessee my mpg dropped since its very hilly. overall the whole trip i did 67.3 mpg but through Tennessee and Kentucky it was tough doing so even at 55mph. top off your tank, run factory tire pressure remove all non essential clutter in the car then try driving 100 miles on the highway at 55 mph cruise control and then top off again see what its at. my diesel compensated for altitude but i could feel a little under normal power compared to my home of Florida
 

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Discussion Starter · #42 ·
ummm 31-35 is not that far off at those speeds when in such hilly highways... when i went to lords town through Tennessee my mpg dropped since its very hilly. overall the whole trip i did 67.3 mpg but through Tennessee and Kentucky it was tough doing so even at 55mph. top off your tank, run factory tire pressure remove all non essential clutter in the car then try driving 100 miles on the highway at 55 mph cruise control and then top off again see what its at. my diesel compensated for altitude but i could feel a little under normal power compared to my home of Florida
Depending on where i go usually i pull out 52 in the hills have since day one, but i have been averaging 42 on the same trip back and forth to work and on the trip to ms same route same speed every time then all of a sudden it dropped now im lucky to pull out 37. I keep track of every tank of fuel and lately it seems to be on the decline for no apparent reason.


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ahh ok so its not so much a gradual decrease its a huge step off. hmm thats a strange one. do you think the computer may not be compensation properly for the high altitude? i could see it running a bit richer then it should thus burning more fuel and more frequent regens
 

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Just an update had the oil changed no metal in it, gonna have it analysed, current hwy milage is around 31- 35 at 85 mph on my current trip seems like my mpgs keep dropping.


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Yeah I just took a long trip down I95 to Miami and set cruise on 80 the whole way and averaged 42 mpg.
 

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ahh ok so its not so much a gradual decrease its a huge step off. hmm thats a strange one. do you think the computer may not be compensation properly for the high altitude? i could see it running a bit richer then it should thus burning more fuel and more frequent regens
Anything under 3,500 ft (1,067 m) is considered low altitude. This has to do with a combination of overall air pressure and partial pressure of water vapor. The interesting thing is that turbo powered cars tend to do better as the altitude increases. This is because the turbo can maintain a consistent air pressure in the cylinders but the aerodynamic drag is reduced.

It's not altitude - something else is going on.
 

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I think the one question that was never asked is about the oil. You indicated that the oil was changed, then the MPG dropped. Improper oil can cause excessive regens which can cause poor fuel economy. Do you know 100% for sure what oil was used?
 

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Discussion Starter · #48 ·
I think the one question that was never asked is about the oil. You indicated that the oil was changed, then the MPG dropped. Improper oil can cause excessive regens which can cause poor fuel economy. Do you know 100% for sure what oil was used?
Yes i used liquimoly top tec 4605 and changed it,


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Discussion Starter · #49 ·
And its dexos2 approved i also just changed he oil again the other day went back to the total and its gotten slightly better economy not much


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I think the one question that was never asked is about the oil. You indicated that the oil was changed, then the MPG dropped. Improper oil can cause excessive regens which can cause poor fuel economy. Do you know 100% for sure what oil was used?

What if the oils original and never been changed ???
 

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And its dexos2 approved i also just changed he oil again the other day went back to the total and its gotten slightly better economy not much


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OK, no issues there. What about fuel? Could biodiesel have been introduced into your fuel supply?
 

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B20 has more potential energy which should translate to better economy.

If anyone has a link that shows more soot being produced from Bio diesel I would like to read it.

Bio cleans everything incredibly well so if you dont use it from new you will get extreme cleaning action that could produce a little extra soot in the short term due to all the dirty deposits getting cleaned out of the fuel system.
My 2 cents.

I would rather run bio to be honest.
 

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I was reading about green diesel sorry bout that, it has has a higher energy density and much higher cetane rating, which should give nice improvement to mileage.
 

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ive not researched it much but i never run bio. here in Florida we have straight diesel. during lords town trip i had to use bio from pumps on highway. not a huge drop that i noticed but i did feel my cruze a bit weaker on throttle.
 

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ive not researched it much but i never run bio. here in Florida we have straight diesel. during lords town trip i had to use bio from pumps on highway. not a huge drop that i noticed but i did feel my cruze a bit weaker on throttle.
Anecdotally and from my "butt dyno", I'd have to agree that non-bio diesel is better from an acceleration standpoint than bio. Still getting frequent regens, but it's only been one tank on non-bio diesel.

Only a real dyno could tell if non-bio is better...
 
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Thanks for that answer...although I realized after I asked the question that I posted it in the wrong thread and deleted the question and asked it in another thread...but yea it seems so simple now....can't believe I couldn't figure it out.
 

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Discussion Starter · #60 ·
Ok so ive narrowed out fuel as a factor, tire drop it by a bit but i was having the issue before they got swapped, no mods, waiting for my oil test to come back


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