21mpg and de-counting

bredi · 01-19-2012, 03:38 PM

I got 42mpg on straight runs from tahoe from sf. 36mpg average when including mountain runs.

34-36mpg on freeway trips.

Then 26-28mpg on a 55% highway / 45% city daily commute.

but...
Now I'm at 21mpg!!! on the same commute!

uh. is this my computer slowly weeding me off my diesel mpg euphoria?

Anyone else see a decline after a few months of ownership? I will say that I noticed a different "cadence" to my engine. Though I couldn't describe the difference.

Diesel fuel quality? winter?

thanks

bredi

F32Fleet · 01-19-2012, 03:43 PM

Could be anything. Idling will surely kill mpgs. Get stuck on one of the many bridges?

Norm4n · 01-19-2012, 03:57 PM

What car is it?

My 335d returns 32 average and that's a mix of town and highway. Plus i have a heavy right foot and I have a remap to 340bhp and 550lbs/ft torques

cssnms · 01-19-2012, 04:29 PM

Could be any number of things,,, e.g. the brand diesel you are running (try switching stations). I see a decline in mpg's during the winter when I run a station's "winter blend." I don't find idling impacts my mpg's all that much since these engines run soooo lean as it is.

igom3 · 01-19-2012, 04:47 PM

My car makes around 23-24mpg around town, and that is with some short trips. Lot of short trips and driving around town (stop lights & signs) will kill your mileage. On the freeway I’m getting 34-37 averaging 70-75mph. Not bad for big diesel IMO

taibanl · 01-19-2012, 08:35 PM

Manually calculate your mileage and report back

scott135i · 01-20-2012, 08:47 PM

When I drive at less than 15 mph (which I do a lot where I live if I am staying local), I get 15mpg or so. On the highway, I get 40-42, with the JBD installed on 100%. That is actual calculated.

bredi · 01-26-2012, 04:16 PM

Quote:

Originally Posted by scott135i

When I drive at less than 15 mph (which I do a lot where I live if I am staying local), I get 15mpg or so. On the highway, I get 40-42, with the JBD installed on 100%. That is actual calculated.

well. I went to another chevron station down the street. My MPG jumped to 26mpg. Which is about normal for my commute. Ideally, I'd be back up a 28mpg.

Bad batch of gas? Winter?

taibanl · 01-27-2012, 06:04 PM

Quote:

Originally Posted by bredi

Quote:

Originally Posted by scott135i

When I drive at less than 15 mph (which I do a lot where I live if I am staying local), I get 15mpg or so. On the highway, I get 40-42, with the JBD installed on 100%. That is actual calculated.

well. I went to another chevron station down the street. My MPG jumped to 26mpg. Which is about normal for my commute. Ideally, I'd be back up a 28mpg.

Bad batch of gas? Winter?

Did u ever do a manual calc?

pjuhlin · 02-15-2012, 01:46 PM

I am getting the same issues with my 09 335 d Sport pacakge 56k miles. I ran down to Vetas and only got 27mpg with mixed driving of 100 mph 25% -70 mph 75% when weather got bad.

kbsilver · 02-16-2012, 07:27 AM

I also have noticed that the diesel seems more sensitive to losing MPG when the engine is cold and stop/start driving than gas engines. With more short around town trips and less highway, my mileage does drop into the mid to upper 20's. But then our 540 does about 16 under the same conditions so guess can't complain. Just for jollies I calculated the ratio of average around town mileage vs best highway mileage for each car. Ratio is similar for both, around 65%.

01-19-2012, 03:38 PM	#1
bredi Private First Class 13 Rep 112 Posts Drives: 335d Join Date: Jul 2011 Location: San Francisco iTrader: (0)	21mpg and de-counting I got 42mpg on straight runs from tahoe from sf. 36mpg average when including mountain runs. 34-36mpg on freeway trips. Then 26-28mpg on a 55% highway / 45% city daily commute. but... Now I'm at 21mpg!!! on the same commute! uh. is this my computer slowly weeding me off my diesel mpg euphoria? Anyone else see a decline after a few months of ownership? I will say that I noticed a different "cadence" to my engine. Though I couldn't describe the difference. Diesel fuel quality? winter? thanks bredi __________________ 2011' 335d M Sport Space Gray/Chestnut/Glacier Everything but Washers 2008' 335i MT Monaco Blue/Black/Dark Burl Sport/Prem/Cold 2004' x3 3.0 MT Gray/Blk/Alum 2000' 328ci MT TIAG/Blk/Alum \| 1986' 325es MT \| 1981' 528i MT
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01-19-2012, 03:43 PM	#2
F32Fleet Lieutenant General 3566 Rep 10,346 Posts Drives: 2015 435i Join Date: May 2005 Location: Southeastern US iTrader: (0)	Could be anything. Idling will surely kill mpgs. Get stuck on one of the many bridges?
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01-19-2012, 03:57 PM	#3
Norm4n New Member 1 Rep 24 Posts Drives: 335d Join Date: Jan 2011 Location: London iTrader: (0)	What car is it? My 335d returns 32 average and that's a mix of town and highway. Plus i have a heavy right foot and I have a remap to 340bhp and 550lbs/ft torques
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01-19-2012, 04:29 PM	#4
cssnms Brigadier General 208 Rep 3,175 Posts Drives: 2011 BMW 335d Join Date: Sep 2010 Location: Murland iTrader: (4)	Could be any number of things,,, e.g. the brand diesel you are running (try switching stations). I see a decline in mpg's during the winter when I run a station's "winter blend." I don't find idling impacts my mpg's all that much since these engines run soooo lean as it is.
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01-19-2012, 04:47 PM	#5
igom3 Major 76 Rep 1,147 Posts Drives: 02 E46M3 15 F80 M3 16 X5 35d Join Date: Mar 2009 Location: San Diego iTrader: (1) Garage List 2016 X5 35d [0.00] 2015 BMW M3 [0.00] 2002 E46 M3 [0.00]	My car makes around 23-24mpg around town, and that is with some short trips. Lot of short trips and driving around town (stop lights & signs) will kill your mileage. On the freeway I’m getting 34-37 averaging 70-75mph. Not bad for big diesel IMO
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01-19-2012, 08:35 PM	#6
taibanl Brigadier General 281 Rep 4,121 Posts Drives: BMW Join Date: Sep 2010 Location: NA iTrader: (4)	Manually calculate your mileage and report back
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01-20-2012, 08:47 PM	#7
scott135i Colonel 355 Rep 2,080 Posts Drives: 2020 X5 M50i Join Date: Feb 2009 Location: NYC Metro iTrader: (12)	When I drive at less than 15 mph (which I do a lot where I live if I am staying local), I get 15mpg or so. On the highway, I get 40-42, with the JBD installed on 100%. That is actual calculated.
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02-15-2012, 01:46 PM	#10
pjuhlin Private 10 Rep 51 Posts Drives: 335D Join Date: Nov 2011 Location: Utah iTrader: (0)	I am getting the same issues with my 09 335 d Sport pacakge 56k miles. I ran down to Vetas and only got 27mpg with mixed driving of 100 mph 25% -70 mph 75% when weather got bad.
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02-16-2012, 07:27 AM	#11
kbsilver Captain 142 Rep 634 Posts Drives: 340GT & '22 eDrive40 Join Date: Jan 2012 Location: North Jersey iTrader: (0)	I also have noticed that the diesel seems more sensitive to losing MPG when the engine is cold and stop/start driving than gas engines. With more short around town trips and less highway, my mileage does drop into the mid to upper 20's. But then our 540 does about 16 under the same conditions so guess can't complain. Just for jollies I calculated the ratio of average around town mileage vs best highway mileage for each car. Ratio is similar for both, around 65%.
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