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E-Class (W211) 2003-2009

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Old 12-14-2009, 03:28 PM   #1
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Arrow mileage increase after glow plugs replaced

My 2006 E320 CDI had a glow plug blow off around 15K - MB replaced the entire set under warranty. However I noticed an interesting thing - My mileage typically was around 27mpg (city/hwy mixed) and now it has shot up to 30 mpg for the same conditions.

Could the glow plug replacement have made the difference or is it that the engine is sort of breaking in around 15K and the mileage is therefore seen to go up. It appears 30mpg is still low by comparison with what others observe on this forum.

On long highway stretches cruising around 65 mph the max I have reached is about 35 during the summer months.
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Old 01-04-2010, 04:13 PM   #2
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bump for any input on this.
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Old 01-04-2010, 04:20 PM   #3
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I don't own any diesel equipment but I have struggled with a lot of it trying to get it going in cold weather. The stuff with glow plugs is a HUGE improvement over heated water jackets , oil dip sticks etc. I cannot fathom why glow plugs which basically become passive after start would affect your mileage. A long shot would be a leak in the head that might have been corrected by new plugs but that is really a stretch. I guess you should simply enjoy your new benefit.
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Old 01-05-2010, 11:30 AM   #4
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Quote:
Originally Posted by Clinton Horn View Post
I don't own any diesel equipment but I have struggled with a lot of it trying to get it going in cold weather. The stuff with glow plugs is a HUGE improvement over heated water jackets , oil dip sticks etc. I cannot fathom why glow plugs which basically become passive after start would affect your mileage. A long shot would be a leak in the head that might have been corrected by new plugs but that is really a stretch. I guess you should simply enjoy your new benefit.
Those are my thoughts... after the engine starts, they are not used, so that milage increase might be placebo effect?
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Old 01-05-2010, 01:06 PM   #5
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Those are my thoughts... after the engine starts, they are not used, so that milage increase might be placebo effect?
I agree with this view. Any possibility that they would have fixed a bad thermostat while working with the glow plugs?
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Old 01-05-2010, 08:44 PM   #6
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Originally Posted by terracotta View Post
My 2006 E320 CDI had a glow plug blow off around 15K - MB replaced the entire set under warranty. However I noticed an interesting thing - My mileage typically was around 27mpg (city/hwy mixed) and now it has shot up to 30 mpg for the same conditions.

Could the glow plug replacement have made the difference or is it that the engine is sort of breaking in around 15K and the mileage is therefore seen to go up. It appears 30mpg is still low by comparison with what others observe on this forum.

On long highway stretches cruising around 65 mph the max I have reached is about 35 during the summer months.
Glow plug should have no effect on MPG. The temperature and fuel would be the factors that will determine you MPG. Have you changed where you buy fuel recently. Some diesel is blended during the cold months based on local climate to lower its cloud point and other suppliers use antigel additives to lower cloud point. The blended fuel will most likely have lower energy content and give less MPG. I can tell with mine by the temperature -- lower the temp lower the MPG.

Make sure you car is reaching operating temperature -- You CDI should be reaching 92C operating temperature. If it is not you need a new thermostat. I noticed when the weather started to get cold my 06 E320 CDI would not get to operating temperature. I put in a new thermostat and it goes to 92C in about 5-7 miles on bitter cold days and stays there. If yours is down around 80c then that is contributing to your lower mileage. With the low miles you have it should not be bad but you never can tell.
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Old 01-06-2010, 12:24 PM   #7
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Originally Posted by Clinton Horn View Post
I cannot fathom why glow plugs which basically become passive after start ...
This is not the case.

Start at page 32 and read on to see about "afterglow."

http://www.mercedestechstore.com/pdf...)%205-5-04.pdf

Plenty of suggestion here that use of glow plugs after start improves engine running, consumption, and emissions.
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Old 01-06-2010, 02:00 PM   #8
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This is not the case.

Start at page 32 and read on to see about "afterglow."

http://www.mercedestechstore.com/pdfs/331_0405update/03-331%20pp%20diesel%20print(FAH)%205-5-04.pdf

Plenty of suggestion here that use of glow plugs after start improves engine running, consumption, and emissions.
Certainly afterglow improves fuel efficiency but the time afterglow is used is so extremely marginal over the whole trip anyone would drive and the efficiency difference from afterglow is nothing extreme, this is why I would conclude "glow plugs have no effect on fuel efficiency". I should perhaps said "glow plugs have no measurable effect on fuel efficiency".
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Old 10-20-2011, 01:31 AM   #9
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glowplugs and mileage

How do I measure that my CDI is reaching 92 deg C operating temps as you suggest?

thanks.

Quote:
Originally Posted by edwinwalke View Post
Glow plug should have no effect on MPG. The temperature and fuel would be the factors that will determine you MPG. Have you changed where you buy fuel recently. Some diesel is blended during the cold months based on local climate to lower its cloud point and other suppliers use antigel additives to lower cloud point. The blended fuel will most likely have lower energy content and give less MPG. I can tell with mine by the temperature -- lower the temp lower the MPG.

Make sure you car is reaching operating temperature -- You CDI should be reaching 92C operating temperature. If it is not you need a new thermostat. I noticed when the weather started to get cold my 06 E320 CDI would not get to operating temperature. I put in a new thermostat and it goes to 92C in about 5-7 miles on bitter cold days and stays there. If yours is down around 80c then that is contributing to your lower mileage. With the low miles you have it should not be bad but you never can tell.
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Old 10-20-2011, 07:47 AM   #10
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Originally Posted by terracotta View Post
How do I measure that my CDI is reaching 92 deg C operating temps as you suggest?

thanks.
Harbor Freight has a sale on IR thermometers. I just had my thermostat replaced as it was hovering around 80 Celcius instead of getting up around 92 Celcisus. I miss the option like I had on my W210, the HVAC controls also gave you access to engine operations IE, TEMP, RPM, Voltage.
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Old 10-20-2011, 11:45 AM   #11
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Originally Posted by 06e320cdi View Post
Harbor Freight has a sale on IR thermometers. I just had my thermostat replaced as it was hovering around 80 Celcius instead of getting up around 92 Celcisus. I miss the option like I had on my W210, the HVAC controls also gave you access to engine operations IE, TEMP, RPM, Voltage.
Do you know if the dealership will replace the thermostat under ELW if it is not going up to 92 deg C?
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Old 01-19-2012, 12:36 AM   #12
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Quote:
Originally Posted by terracotta View Post
My 2006 E320 CDI had a glow plug blow off around 15K - MB replaced the entire set under warranty. However I noticed an interesting thing -
My mileage typically was around 27mpg (city/hwy mixed) and now it has shot up to 30 mpg for the same conditions.

Could the glow plug replacement have made the difference or is it that the engine is sort of
breaking in around 15K and the mileage is therefore seen to go up.
It appears 30mpg is still low by comparison with what others observe on this forum. [Sure is!]

On long highway stretches cruising around 65 mph, the max I have reached is about 35 during the summer months.


So in December, 2009 you only have 15K miles on a 2006 CDI?

Things to remember about diesels, especially with the VW TDIs.
That group does not consider their motors to be completely broken-in until 50 to 60K miles.
Could our CDIs fit into that group also? If so, you've got a ways to go.

Just last month, I bought this example:

http://www.autotrader.com/fyc/vdp.js...standard=false

We travel about 2K per month, so it now has 111,700 miles on the odometer.
I have so far made three detailed F E checks on it, and the last one was 37.1 MPG for 463 miles.
Not computer readings mind you, but actual tank mileage figured with gallons used over miles traveled.
Maybe it helps to have over 111K miles on the motor?

See my Fuelly:

http://www.fuelly.com/driver/derrelhgreen/E320
All of this so far with a stuck open thermostat, with the temperature gauge sometimes reading only
40 C. when it is cold at night on the interstate. Should be up in the low 90s C. correct?

In the winter, do not expect as good F E as you will see in the summer. Winterized fuel don't you know?

Bad thermostat and a leaking fuel injector that leaks diesel exhaust where the injector goes into the
cylinder head holpefully will be fixed tomorrow. Maybe then my F E will go up even a little bit higher?

How is your tire PSI and alighment? That can make a little bit of difference also.

Wish me luck tomorrow.



Derrel

Last edited by Green E-300 DT; 01-19-2012 at 12:39 AM.
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Old 01-19-2012, 12:36 AM
 
 
 
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affect, cdi, diesel, e320, e320cdi, glow, increase, mileage, operation, plug, plugs, proper, replacemnt, running, thermostat, w211



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