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Old 12-22-2000, 07:59 PM
Registered User
Join Date: Nov 1999
Location: Santa Cruz, CA USA
Posts: 117
My wife teases me 'cause I refer to Mercedesshop as "Group Therapy", so I'm going to ask the group a question...

I have an 86 300e with 89,000 on the clock. I drive 90 miles a day. 45 each way to work on the open freeway. Not too many hills. Mostly an easy and clear shot along the Pacific Coast Highway. If I'm doing really well, with the tires perfectly inflated, with high grade gasoline and fresh oil, I can maybe get 25 MPG out of a tank. That's with perfect conditions. I would like to squeeze another couple of miles out of there. I was thinking,
Would a hotter sparking coil do the trick? I use Non-platnum Bosch plugs. Are there better? Is there a front spoiler that would keep air from under the car? Would this do anything anyway? I have read posts from some of you about some oil additive... I can't remember the name. Do some of you 300e drivers have any tricks or is 25 MPG about what I'm stuck with.
Kyle De Priest
2007 e320 Bluetec
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Old 12-22-2000, 08:19 PM
JCE's Avatar
JCE JCE is offline
Down to the Wear Bars
Join Date: May 1999
Location: So Kalifornia
Posts: 2,189

Lets trsde! My 87 300e (71,000 miles) once got 22 mpg as it's personal best on a run to SF at 70 mph. I seem to get around 19-20 overall combined freeway and city. I wouldn't mind your mileage at all.
After all, this is 3 liters geared more for performance than economy, and pulling close to 3500 pounds around! I guess trading for a later w124 E320 with the m104 engine, or trading for the diesel, would get you better mileage. Alternatively, switching to Michelin Energy tires might up the mpg up by 3-5%, but the trade off would be performance and handling.
I like the performance, and am willing to sacrifice a little comfort, mpg, and tire life for handling. Have a great Holiday!!

2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)

Click to see 87 300E
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Old 12-22-2000, 08:36 PM
dakota's Avatar
Moof !
Join Date: Jul 2000
Location: Seattle WA USA
Posts: 469
Synthetic Oil

With my '90 300E, I have obtained a consistant 25-27 mpg at 75-90 mph with the A/C on. I use synthetic oil (Mobil 1 10w30) and a K&N air filter.

I don't think I would fool with the ignition system, but those MSD systems or Jacobs Omni Magnum units look interesting....I think some have reported that they helped (comments, Donald?).

You could probably help by lowering the car a bit, but I'm not sure what would be involved and if it would be worth it.

I think the synthetic oil might be your best bet (cost vs benefit). It's not a big investment to try it out, and it definately should not make your mileage worse, unlike what might happen with other attempted "fixes".

Just my 2 cents. YMMV :-)
1992 300CE Sportline Sophie
1990 300E Emma - in the family
1979 240D Josephine - sold, but not forgotten
2004 Pacifica AWD
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Old 12-22-2000, 09:05 PM
Registered User
Join Date: Nov 1999
Location: Santa Cruz, CA USA
Posts: 117
Thanks for the responses... I average about 21 to 23 with the car right now. Lowering the car is an interesting idea. I love the way it rides now and I really enjoy driving it. It's just that the gasoline is killing me... especially at close to 2 bucks a gallon!
As far as synthetic oil goes, I was a strong advicate of the stuff. Not to start another thread on this subject, but when I first got my car at 62,800 miles on it, I switched to synthetic immediately. I thought, this car is going to live forever!!! Well, the car sprang more leaks than you can believe. Like crazy, all the oil that ran out of there. I talked to a MB tech and he told me to switch back and see what happens. I did, and the engine is clean now. I might look into the lowering idea. How about the low spoiler? (not one that looks obvious, I hate that stupid stuff) just a black one under there?
Any thoughts?
Kyle De Priest
2007 e320 Bluetec
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Old 12-22-2000, 11:00 PM
Posts: n/a
Let's wean the Baby

Kyle DePriest, I have a 1987 300E with 169,000 miles.Let me tell you what I've done to improve my fuel consumption.
1) removed mid-muffler. Replaced with 3" Y pipe
2) Jacob's Ignition System
3) K&N Air filter element
4) 8mm silicone spark plug wires
5) Copper cored spark plugs gapped at 0.052 inches
6) Wrapped the exhaust manifold with insulating materials
7) Inflated tires to 35psig
8) No full throttle starts
9) Learn new driving habits
10) Use the A/C only when needed
With all of these and there may be more, for calender year 1999,my overall mpg was 19.9. Boy would I like to get 22mpg let alone 25 and want 2mpg more.

I just can't cut it
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Old 12-23-2000, 12:09 AM
Registered User
Join Date: Nov 2000
Location: Tribune, Kansas. I farm for a living. I fly R/C airplanes for fun.
Posts: 53
Wow. I just took a trip of 275 miles via interstate and regular two lane roads, mostly at 75mph and a light crosswind, and got 26.6 with my 1986 300E. I guess I have no complaints, or better not have anyway about my mileage.
Ron Miller

1986 300E
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Old 12-23-2000, 11:23 AM
Posts: n/a
I get from 25 to 27, but mine's a stick, so you would expect it to be a little better. But, still your fuel mileage does sound like it's a little off.

Do you have fresh plugs, air filter and everything running right?

Good luck and Merry Christmas,
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Old 12-23-2000, 12:01 PM
Posts: n/a
Hey Gang, I Said Average

Depriest, My reply to you was my annual mpg average was 19.9. When you consider that at least 75% of my driving is in the city, my mileage is outstanding in my reasoning. I get the mid to high twenties on the road, at the speeds that don't get me in trouble with the Law. When the 300 was new, it got the same mileage as it gets now after all of the rinky dink changes I've made. But mileage isn't the whole story. Performance is what I've gotten in return. It sure runs super. So you see I've got both, good economy and improved performance but it didn't come easy or cheap. Here's hoping you decide which one you want or maybe both. Happy Trails Beep Beep from Houston.

as pleased as can be
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Old 12-23-2000, 12:17 PM
Posts: n/a
dakota Ignition System

I am using the Jacob Magnum Ignition System. My performance has improved in the areas the unit is supposed to. 1)easier starting, hot and cold 2)improved throttle response 3)better fuel economy 4)higher rpm without ignition break down 5)engine lugging without spark failure 6)a real pretty thing under the hood, it's blue and it hamonizes with the maroon of the car color. If I had it to do over or would I choose the MSD(I have it on my other Germain car) I'll go for the Jacobs rather than a capacitor discharge unit. You should get the info from Jacobs, good reading. Happy Trails Beep Beep from Houston.

just another hot wire
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Old 12-24-2000, 11:01 PM
Ian Parker
Posts: n/a
More Ideas

I am not familiar with some of the details of your MB but there are a couple of things I have done in the past which have been very effective.
If the cooling system has an engine driven fan whether thermostatic or strictly mechanical, try removing it. You can get away with this in cooler weather and if you never spend too much time stuck in traffic. If it works, look into an electric fan or a manual override for the electric fan if your 300 has one (our 88 300TE has an auxilary electric pusher fan). I had amazing luck with a Fiat 128 fan on a couple of Volvos we had (3 to 5 mpg improvement).
Also, learn how to adjust the fuel injection system for overall mixture. The basic Bosch mechanical systems use a 3mm allen key (a long one) and the adjustment is betweed the big dash-pot and the fuel distributor. Only go in very small increments, approximately 1/8th of a turn at a time and keep a record of where you are at relative to where you started. Drive it for a couple of days and see if there is a difference. It is much easier to feel the difference than you would expect. CCW is leaner, CW is richer.
Have you changed the O2 sensor. You can get a Bosch universal for about $50.00 or so. These come with a short set of leads you splice into the original cable. Waaayyy cheaper than buying the OEM sensor and factory leads.
Good luck.
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Old 12-26-2000, 03:13 PM
Posts: n/a
You have looked into my box

Ian, you must have looked into my box of things to do. I have a 16" thermo controlled electric fan to replace the mechanical beast, just haven't installed it yet. That looong allen wrench adjustment on my 300E is the Lambda adjustment for the fuel mixture adjusting the output voltage from the O2 sensor and makes for a smooth idle. One item I'm working on and have had good results from on carb equipt domestics is Water infection. I'm almost there. Happy Trails and New Year Beep Beep from out foxed Houston.

oh what fun it is or will be or whatever
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