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2002 E320 4Matic Wagon
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Discussion Starter #1
Broomhilda - our silver '02 4Matic wagon - just turned 100K miles. We bought her at 72K miles (with help from the good folks on this forum). Wonderful car.

Her highway gas mileage has declined from 28 - 30 MPG to about 22 - 24 MPG. I checked for powertrain codes this morning; nothing!

So, in addition to new spark plugs (NGK 7090 suggested? Connectors required?) and new air filter (it was also done 20K miles ago), is there anything else that should be replaced?

- Do 02 sensors effect e320 MPG without showing codes?
- Ditto the e320 MAF sensor?

BTW, I tried cleaning the MAF's (2) on out '00 BMW M5, no improvement; and ended up replacing them.

Is cleaning the E320 MAF recommended if no codes?

BTW also, Broom has new michelins at 30/34 psi ft/rear. I double checked the mpg on our thanksgiving road trip to Pauleys Island; ~ 400 miles at 60 MPH; very gentle driving. 2 people; 2 dogs ; )

Our M5 gets ~ 25 MPG hiway (and it has 400+ hp!)
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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17,193 Posts
If you can believe Bosch your O2 sensors are due at 100,000 miles. If they are out of range they will affect your MPG. The only time I had a CEL it was due to a bad oxygen sensor.
 

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E320/E250 Bluetec Ford F350 6.7l
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When I had gasser wagon, the MAF replacement gave me almost 15% mpg increase. Worth trying, the worse thing might happen is that you will end up with spare MAF, what is not bad option ;)
Consider that our government is playing with fuel. I know CA gasoline had 7% of alcohol years ago what was one of the reasons I switched exclusively to diesels, since my wagon couldn't make 20 mpg on the STUFF bought at CA gas pumps.
Per my knowledge CA gasoline has about 10% of alcohol right now and lot of states follow.
 

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1997 E320, 1997 S320
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2,946 Posts
do you always fill with gas at the same station or same brand? try switching brand/station and see if that helps. not sure if they change gas formulation according to seasons in nc, but here in the midwest we get winter and summer gas formulation. winter gas starts in sept/oct until april/may, and i always get 20-30 miles less of a tank than i do with summer gas.
i wouldn't bother cleaning the maf, and change air filter only if it's really dirty and not by mileage. bad o2 sensors will give you codes, i am at over 200k miles with original o2 sensors and no change in mpg. if it's not because of different gas, most likely the cause is the plugs in my opinion, especially since they are due to be changed at 100k miles. i think all you need to replace in your engine is the plugs, and no connectors or wires.
 

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1997 E320, 1997 S320
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Per my knowledge CA gasoline has about 10% of alcohol right now and lot of states follow.
a few states can have up to 10% ethanol content in gasoline and are not required by law to say it on the pump. in my state only the middle grade (89) has 10% etoh while regular (87) and premium (91) don't have etoh. a few gas stations have 10% etoh in all grades, but they all say it on the pump next to the grade. last year on a ski trip to colorado i filled up at a gas station and it didn't say it had any etoh on the pump. when i asked the guy at the cash register he said all their gas has 10% etoh, but they are not required to say it on the pump. i'm affraid pretty soon all states will have 10% etoh in their gas:(
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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You have a 4 - matic and efficiency losses with be accentuated/multiplied as compared to RWD. Actually unfoar to compare the mileage of a 4 matic wagon to your M5, totally fair to compare your M5 mileage to a E55

1) Sure, you can do a pre-emptive MAF replacement as long as it is a genuine Bosch replacement (autohausaz.com). I normally do my MAF at 125K, however I am not a mileage tracker kind of guy.

2) Spark plugs, no reason to go for other than the updated version of the standard Bosch FR8DP33 - if they were good for 100K, why even break a sweat over a alternate replacement. However, on DIY I HIGHLY recommend the "MB boot removal tool" PM ohlord for this handy dandy.

3) Of COURSE replace your air filter, which to maximize mileage I would recomend you should replace at every 10K oil change. The OE Mann only, aftermarket about $16

4) You have your tires at closer MB spec, I do too, honestly your fronts are low about 2-3 lbs my opinion. The point here is your mileage will go down as the tires wear. I am also saying maximum MPG and driver feel are sometimes contrary.

5) I would recommend a regimen of fuel system cleaning, either a large bottle of Techron 2 or 3 tanks before oil change, or more regular use of the Lucas product every 10th tank or so ($13 a large bottle for 4/5 applications).

6) Pre-emptive front O2 sensor replacement can be considered to maximize milage, try amazon.com for best pricing for pllug-n-play Bosch replacements.

Personally, I don't trust cat's on the wagons, but that's me.
 

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1999 E300 TD
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2,045 Posts
Just because you had a bad day sailing, don't take out on "Broomhilda."

Think about this, first how do you know what your gas mileage really is!, over what conditions, compared to what, for how long, where, what time of day, who's driving, type of gasoline.

Then add to that all the mechanical things you can control and can't control.

I believe that before you start with the cold war mentality of cleaning every sensor on the car to try to improve gas mileage will result in lower mileage, damaged sensors and cost more money in the long run.

Remember you car has an engine management system with stored values to use when sensors produce out of range data which result in a check engine light. THAT is the time to change the sensor, when it's bad. DON'T so called clean them, especially the MAF which is a very expensive sensitive sensor, because the alternative would be to walk the dog..

Think about this one, what would you do if one month you used more electricity than the previous month---change all the appliances, rip out all the lighting!! I don't think so.

Go sailing, "Broomhilda" will provide many more good days of transportation and when she needs your help she will tell you----"CEL"

Good luck!!
 

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2002 E320 4Matic Wagon
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118 Posts
Discussion Starter #8
Thanks...Compliments...A Game Plan

Thanks everyone. I love this forum!

Gameplan is that I'll change plugs and filters, checking mileage before and after. If still an issue, I'll try progressively techtron, 02 sensors and an MAF. I will report results here.

The cats were dealer replaced (rattles) about 25K miles ago. I will try a little more air in the tires also, though the front seems to be happy at 30 psi. I experimented with tire pressure before finally replacing the front struts (with Bilstein OE).

Comments:
I checked the MPG when we first got Broom, and it consistently ran 28 - 30 MPG on the highway. We bought a 4Matic only because it was the best E320 wagon example we could find (test drove a number of kinda ratty RWD's first). I was pleased with the MPG, and am now REALLY glad we got a 4WD. Broom is an absolute goat on flyfishing backroads and snowy driveways.

Generally, my wife drives Broom; and (as a budding bluegrass fiddler), she makes 600 mile monthly round trips to our VA mountain house (Stuart, Virginia). She's been telling me about poor gas mileage now for about 4 months, but - being the artsy type - never really knew the numbers. I finally checked and found 22 - 24 MPG tops.

NC is progressively joining the Liquid Farm Aid bandwagon, by way of ethanol in gas. As it relates to MPG, this is a really good point, and something I had completely missed.

Last time I checked, ethanol had roughly half the enthalpy of gasoline. So, 10% ethanol would mean about 5% less BTU/gallon - and , consequently, about a 5% drop in MPG. A really good point. This, coupled with the negative net energy equation associated with ethanol production, makes me a real fan of the whole ethanol concept.

Broom gets gas wherever, but always premium. In NC, seems that the major gas brand stations have kinda gone South. I don't know whether the pumps are marked for ethanol, but I'll start looking from now on.
 

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99 E430, 01 E430 Sport, 00 SL500
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You do different things to fix depending on how the gas mileage dropped, sudden drop or gradual drop.
 

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2001 E320 4-Matic
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81 Posts
Newbie Babble...

My '01 E320 4-Matic averages 27.5 on Hwy trips around 70-75. In the summer I was averaging 22-24mpg on my 40 mile round-trip drive from home to work and back. 50/50 split city-hwy. Now with winter fuel blend, it is 20-22. I check tire pressures monthly and go with the fuel door sticker of 28/34 psi. While this is not earth shattering, my previous car, a '00 Accord v6, got identical mileage, was 400 lbs lighter and had 10% less power. Tire pressure on that car was easy- 32lbs all around.

The champ though was our '98 BMW 528i- it averaged 34+ mpg on the highway, and 24-26 mpg in the city.

I lost in my LR3 1.5mpg, when I switched to GC 0w-30 as it is a GF-3, not a GF-4. Also when I switched tires I gained a 1 mpg. The o2 angle is possible, as they do default to rich as they age. Not one thing is going to gain you a huge benefit, it is definitely a combination of 'things.'

Ethanol 10% takes 1mpg from mine as well. There are only 3 gas stations that I fill my car at, makes it easier for me to be consistent, and they are on my typical routes etc.
 

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W210.265/2001, W220/S500/2000, Porsche 997 C2S/2006, GMC K1500/1992
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If you get around 22-24 mpg it is very good. I own my E320/01, RWD, since new. Average MPG is around 22.5. I always push the car to 85 mph in city highways. I will not mess with any sensors if car achieved 24mpg.
 

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E320/E250 Bluetec Ford F350 6.7l
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Ethanol 10% takes 1mpg from mine as well. There are only 3 gas stations that I fill my car at, makes it easier for me to be consistent, and they are on my typical routes etc.
Few years back while driving gasser to Arizona, I experienced at least 15% mpg gain on AZ fuel. That equals to at least 3 mpg.
All regardless the fact that in AZ I always drove faster than in California.
Nevada is selling CA refined fuel, so not big difference there.
 

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2001 E320 - Brilliant Silver/Ash: 107,000+
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All the stations here have been forced (by some government agency that I assume is the EPA) to switch to "This fuel contains up to 10% ethanol". I don't notice any difference in MPG in any of my 3 cars but they don't seem to run quite as well.
 

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99 E430, 01 E430 Sport, 00 SL500
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When I went up to Big Bear mountain for skiing, the fuel gauge went down noticeably. On the way home in the valley, the gas mileage went up like 15%. So did the snow help or hurt the gas mileage?
 
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