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  #1  
Old 10-06-2002, 11:43 PM
unkl300d's Avatar
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Location: San Francisco, Ca
Posts: 2,275
Thumbs up Exceptional gas milage or a fluke?

Today, I filled my 300D up, 101.3 miles after the last fill up.

It took 2.027 gallons until it was overfilled.

Do the math.

You see , I recently had the injectors changed and I was taking the MPG to compare with past performance.

After 207 miles I filled it up and calculated 16.41 MPG.
Looked under hood and saw that the end cap (injector by pass hose) was leaking.
Got that fixed, filled up and ran another 125.3 miles. Filled it up again and calculated 17.1 MPG.
Still below my past averages.

Between this last fill up and today's I observed the above
data.
My odometer concurs with the trip odometer.
My notes concur also.
The tank was filled to the brim, concurred by the fuel gauge above the full mark.
Even if I were able to squeeze in another gallon, that would be
33.7 MPG.

The driving scenario was mmostly freeway combined with some city driving.

Too good to be true.
But I share the anecdote.

I will continue to observe the future fuel usage.
__________________
1979 300D 199 K miles
1995 C280 95 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD
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  #2  
Old 10-07-2002, 01:22 AM
Mercedes Diesels Forever
 
Join Date: Oct 2002
Location: Boston, MA
Posts: 42
The best way to check MPG is use the mile markers on the highway for several miles to check your odomo and head to the diesel station. When you refill, have the fuel level three inches from the top. Record amount of gas.
Go to highway markers again, and then go to a different station, fill up again.
Use you calculator on the your computer to calculate MPG. The figures should be the same. Post results on forums..

Bill
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  #3  
Old 10-07-2002, 01:34 AM
the_good_fellow's Avatar
07 E320 Bluetec 7 pistons
 
Join Date: Jul 2001
Location: Houston, TX
Posts: 170
My 300SD is getting 30+ MRG in normal 60/40 hwy/city driving Lately. I don't know why. I used to fill up every 7-8 days, now every 10-11 days

Here are something I've done:

Back in Jan I installed a home made Boost Controller, and disconnected the EGR. I got about 23/24 MPG.

In March I adjusted the valves(most of them were very tight) and Oil changed. I got 24/25 MPG.

At the end of April I installed a K&N AF and modified the blow by oil collector to prevent too much oil going to the AF. Reconnect A/C wire(has it disconnected forwinter) and the A/C Comp locked up. Since then I haven't driven it that much(mostly city in the evening)but I have noticed each tank I got about 27 MPG.

In AUG I finally got a new A/C comp installed so i use it more often. And every tank I got 500+ miles with 17+ gal fill up.

my last two fill ups:
17.35 G and I got 535 miles ~ 30.84
20.20 G and I got 624 miles ~ 30.89

My boost is set at 14psi and It's 15" 205/65 tires before all these.
what's the mileage error with over size tires??? can someone help figure this out?
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BJ

09 GL320 Bluetec 65K+
07 E320 Bluetec 43k+
05 Nissan Frontier NISMO 4X4 72K+


07 Kawasaki Vulcan 900 5k+ gone
87 300SDL 158k+ gone
91 300D 113k+ gone
83 300SD 220K+ gone
89 300E sold
87 190E sold
83 380SEL sold

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  #4  
Old 10-07-2002, 06:52 AM
junior member
 
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Posts: 592
tire size/mileage

http://www.miata.net/garage/tirecalc.html
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  #5  
Old 10-07-2002, 12:02 PM
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Join Date: Dec 2001
Location: Connecticut
Posts: 20
mileage on 300TD

My last 5 tankfuls have given me an average of 28.5 mpg. That's city and highway. I've yet to go on an all highway trip. Top speed for me is 65 mph.
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  #6  
Old 10-07-2002, 01:49 PM
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Location: Fairfax County, Virginia
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I have had two 300Ds and a 350 SDL ... very little difference between highway (usually 75-80 mph = 26 MPG) and mix of city/highway commuting miles (=24-25 MPG) ... I am sure I could get 30 MPG, but would need to maintain 55 on the highway to do it.

As far as getting above 32 or so in a 123 or 126 ... nah. Likely to be some foaming that is causing premature fill indications.

Do the math over about ten tanks and see what it is ... should average out any errors.
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #7  
Old 10-07-2002, 02:21 PM
markluta
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I agree with the above post. My 300SD does 24mpg with mostly city driving and a/c on, 26mpg on highway in cool weather. And there is a definite drop off in fuel efficiency when driving over 80mph for long periods of time, so 55mpg would probably get 27, maybe 28mpg. And I mostly fill up at the same station, always fill until I can see the diesel so it is about the same place, and the numbers are really consistent. So, no way does any stock 300SD get over 30mpg.
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  #8  
Old 10-07-2002, 10:49 PM
Robert W. Roe's Avatar
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Join Date: May 1999
Location: Lehigh Valley PA
Posts: 1,322
Man, I want one of these 30 mpg diesels!
The two gallon 50 mpg figure is a most likely a statistical fluke.
Been there done that.
The car mags average out fuel consumption over a full year.
I started keeping an Excel spreadsheet tracking my fuel purchases and was averaging just over 20 mpg.
I haven't kept up with my data entry, having just bought a house, and trying to sell my old house. Maybe after I have some $$$ I might try to tune up the old SD, or get a newer car of some type, maybe a TD wagon.
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Bob Roe
Lehigh Valley PA USA
73 Olds 88, 72 MB 280SE, 78 Datsun 280Z, 71 T-Bird, 72 Olds 88, 83 Nissan Sentra, 85 Sentra, 73 230.6, 91 Integra, 83 300SD, 91 Volvo 940GLE wagon, 84 300SD, 95 Subaru Legacy L wagon, 02 Mountaineer, 91 300TE, 08 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon all gone... currently
2007 Honda Odyssey Touring, 2011 Honda Odyssey Touring
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  #9  
Old 10-08-2002, 12:30 AM
unkl300d's Avatar
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Location: San Francisco, Ca
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Play it again Sam

I suspected back pressure causing a 'false fill up'.
It was not foam because I waited and pushed the rear up and down to shake the fuel down.
Nontheless, I suspect something fishy.

The odometer is fine and the fuel gauge seems fine, but I still think it is a fluke.
Yes, I'll see over time what happens.

I can get 25MPG on all freeway driving as well.
So, if I would have been able to squeeze in two more gallons
beyond the 'apparent' fill up, then it would have panned out at 25MPG.

We shall see.............
__________________
1979 300D 199 K miles
1995 C280 95 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD
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  #10  
Old 10-08-2002, 12:39 AM
Robert W. Roe's Avatar
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Location: Lehigh Valley PA
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Oh, with respect to the tire size question, I remember calculating this once before for 205-65/15 vs 195-70/14 and the 15's were about 3% larger, so 300 miles indicated is really 309 or so. Or 20 mpg is really 20.6 mpg.
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Bob Roe
Lehigh Valley PA USA
73 Olds 88, 72 MB 280SE, 78 Datsun 280Z, 71 T-Bird, 72 Olds 88, 83 Nissan Sentra, 85 Sentra, 73 230.6, 91 Integra, 83 300SD, 91 Volvo 940GLE wagon, 84 300SD, 95 Subaru Legacy L wagon, 02 Mountaineer, 91 300TE, 08 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon all gone... currently
2007 Honda Odyssey Touring, 2011 Honda Odyssey Touring
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  #11  
Old 10-08-2002, 02:16 PM
angst's Avatar
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Quote__________At the end of April I installed a K&N AF and modified the blow by oil collector to prevent too much oil going to the AF. Reconnect A/C wire(has it disconnected forwinter) and the A/C Comp locked up. Since then I haven't driven it that much(mostly city in the evening)but I have noticed each tank I got about 27 MPG_______

Describe your oil blow by tube mod.

I did an intake mod that some might find interesting. I have a K+N but I did not have the car long enough before doing this mod to get a mileage baseline. The bigger intake did help the pickup up at low speeds.

http://kayakoutfitting.com/mercedes/intake.html

Eric z
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  #12  
Old 10-08-2002, 03:28 PM
turbodiesel
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I always get 22mpg with mine, no matter what I do.
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  #13  
Old 10-08-2002, 03:54 PM
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Location: Fairfax County, Virginia
Posts: 856
Just FYI, but seems like I recall that free flow air filters will make a difference ONLY at full throttle ... maybe it was Pat Goss? So, if you drive at full throttle only occasionally, it likely is, again, on the margin (admittedly, we drive at full throttle more often in diesel cars than in gas power cars).
__________________
George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #14  
Old 10-08-2002, 10:16 PM
CJ CJ is offline
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I agree, the free flow filters will not really make a noticable difference on a MBZ diesel engine.
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  #15  
Old 10-09-2002, 01:22 AM
the_good_fellow's Avatar
07 E320 Bluetec 7 pistons
 
Join Date: Jul 2001
Location: Houston, TX
Posts: 170
I agree with the mpg(23/28 city/hwy) most of you're getting. That's what I used to get since I bought it six years ago. It's still a puzzle to me at this point. It's the 1st time I got over 600 miles a tank. I'll keep you guys update on next fill up.

BTW 300D gives me 25/34 (K&N doesn't help much, may be some mod.) and 300 SDL gets 23/27

Eric,

To reduce the blow-by you will need to take the air filter cover off. remove the lid of the oil collector/separator where the breather hose connected to. If my memory serve the tube is about 1~2" deep and it's blocked by a little fin at the end which prevents the oil from free fall. it may splash all over the place too if you rev eng. I removed the fin and connect a high temperature oil hose to the tube and secured it with a clamp. the other end of the hose is barely touching the drain hole. that way oil can drip directly into the drain hole and the vapourize oil can escape. I took the elbow hose off this evening and there is no more oil near the turbo inlet.

oil in compressed air does reduce the amount of oxygen molecules intake which reduces the efficiency of the combustion.
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BJ

09 GL320 Bluetec 65K+
07 E320 Bluetec 43k+
05 Nissan Frontier NISMO 4X4 72K+


07 Kawasaki Vulcan 900 5k+ gone
87 300SDL 158k+ gone
91 300D 113k+ gone
83 300SD 220K+ gone
89 300E sold
87 190E sold
83 380SEL sold

http://banners.wunderground.com/bann...TX/Houston.gif
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