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  #1  
Old 10-24-2005, 02:17 PM
Diesel Dad
 
Join Date: Sep 2005
Location: Santa Cruz, CA
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1985 300TD - How can I increase my MPG?

Driving to work today, I noticed a bunch of extra stuff in the back of my wagon that I should take out to lighten the load

I'm getting between 20-22.5 MPG which isn't bad, but there can always be room for improvement.

Any ideas? I'm new to the MB world,

Hugh

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  #2  
Old 10-24-2005, 02:26 PM
boneheaddoctor's Avatar
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You should leave the 30' cabin cruizer parked in the lot and not tow it everywhere.

other than that make sure its properly tuned and adjusted.
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  #3  
Old 10-24-2005, 03:44 PM
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mix in veggie or At oil.
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  #4  
Old 10-24-2005, 05:10 PM
cmichalik
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I switched from Dino oil to Rotella Syth oil & jumped 4 mpg. Although it didn't happen over night. It happened after running about 1500 miles.

A few weeks later I noticed I was a little low on air in the tires, so I air them up a little more than spec and got another 1 mpg out of that. I'm currently running 30 mpg doing 80% hwy driving at 55mph. It take a LOT of self control to drive 55 when everyone is passing me doing 60+.
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  #5  
Old 10-24-2005, 06:06 PM
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Quickest increase in MPG - put it up on eBay...seems they start getting upwards of 40 mpg nowadays.
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  #6  
Old 10-24-2005, 10:21 PM
Waitn For The Bus All Day
 
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Location: south east pa.
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I've got the same car and consistently get 28 MPG and as much as 31.8. Not much traffic here...that helps.

In a high traffic area my mileage will drop to 23 or so.

Drive with a light foot. Take off slow and coast to a stop.

Did you check for fuel leaks such as the return lines?

Cheers,

Bill
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  #7  
Old 10-25-2005, 01:38 AM
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My 85 wagon consistantly gets 25mpg in mostly city driving. Haven't done a long highway test yet. It pulls too hard to the right to do any long distance driving yet.

The smoker (non turbo) used to get around 22-24 until it started smoking so badly. now it gets around 17-19
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  #8  
Old 10-25-2005, 09:15 AM
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FUEL mileage increase...

You might try decreasing the aero drag. You can reduce the front ride height about 1 to 2 inches lower than the back. Or try making a front spoiler that will go down from the front pannel about one to 2 inches. If your back bumper can act as a "cow catcher" type air drag....put a level pannel from it's lower edge on towards the front of the car and try to keep air out of the area. You can make a small wind splitter in front of the rear tires (runs vertically and pushes air around the tire) that is not too visible....helps air to flow around the rear tires. Then wax that car to the hilt. Waxing and polishing is supposedly good for 1/2 to 1 mpg on the average car. Use rain-x or a product for the glass from "For my Mercedes. c o m"....leave out the spaces. Jerry's stuff really cuts the friction on the window glass....your windows will go up and down faster on those cars with really tight side glass seals as proof....stopped a window squeek on raising/lowering that way. His pollimer wax is good stuff as well.

Studies undertaken during gas crisis one (1972) showed that the side mirrors on cars was responsible for about 1/2 to 1 mpg decrease per car.....and the govt. tried to figure a way for rear viewing without the mirrors, but nothing ever came of it. Today, the same study might result in small tv. cameras and a interior view screen instead of the side mirrors. Pougeot did an aero experiment using simple tricks such as these and that car did not look too far from the average car, and got the aero down less than 30. Audi paid attention and then their flush side windows of the early 80's came about. The railroad cross tie bumpers on American cars of the 70/80's really hurt aero....in that they overhung the body on the sides. Those styles have pretty much gone away-even on the SUV/trucklets.

Regards

Run-em
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  #9  
Old 10-25-2005, 09:41 AM
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Join Date: Apr 2005
Location: Eastern Long Island
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Rear End Ratio

I just switched my axles out for some CVJ rebuilds, and noticed the rear end ratio etched on the bevel gear of the differential. I have a 2.66:1 rear end which must be close to the tallest that they made. I am not a slow driver (I put my foot into it fairly regularly) and have been getting 27-29 MPG in mixed city & country driving.

I have a friend with the same car and he is getting 22 MPG.

Changing the axles was not so bad. I don't think that changing the rear end would be much worse. I know that if that was the only contributing factor to the difference in fuel mileage. (which I know that it is not) this would contribute to around a 40% change in fuel economy.
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  #10  
Old 10-26-2005, 03:25 AM
Diesel Dad
 
Join Date: Sep 2005
Location: Santa Cruz, CA
Posts: 48
properly tuned?

Quote:
Originally Posted by boneheaddoctor
make sure its properly tuned and adjusted.
Not sure what this means? What all should I check?

so far, I've changed the oil and filter (Rotella T 15-40W), both fuel filters, breather hose and air filter.

I do a lot of in town driving , but I did go 350 miles on the freeway and got 22.5 mpg.

Hoping to get 25+ mpg,

Hugh
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  #11  
Old 10-26-2005, 08:59 AM
Waitn For The Bus All Day
 
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Location: south east pa.
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Quote:
Originally Posted by Hugh_Benz
Not sure what this means? What all should I check?

so far, I've changed the oil and filter (Rotella T 15-40W), both fuel filters, breather hose and air filter.

I do a lot of in town driving , but I did go 350 miles on the freeway and got 22.5 mpg.

Hoping to get 25+ mpg,

Hugh
And it should be mentioned here that Santa Cruz is very hilly in town driving and if you do 70 MPH on the freeway you'll get run over.

Cheers,

Bill
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  #12  
Old 10-26-2005, 09:38 AM
boneheaddoctor's Avatar
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Quote:
Originally Posted by Hugh_Benz
Not sure what this means? What all should I check?

so far, I've changed the oil and filter (Rotella T 15-40W), both fuel filters, breather hose and air filter.

I do a lot of in town driving , but I did go 350 miles on the freeway and got 22.5 mpg.

Hoping to get 25+ mpg,

Hugh
Mainly what that means is make sur eyou timing chain stretch is at a minimum...make sure your valves are properly adjusted....your filters are clean, you car has a good alignment and your tire pressures are what they should be.

If you drive mountains expect lower milage...Not familiar with your area but I have seen 29 mpg with my W123 driving to and from Bill Murows place...mostly highway with no big hills.

Lastly smoth motions driving...IE no more go pedal than needed...
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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
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  #13  
Old 10-26-2005, 09:40 AM
dannym's Avatar
I'm not here
 
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Location: Deltona, Florida
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Quote:
Originally Posted by Hugh_Benz
Not sure what this means? What all should I check?

so far, I've changed the oil and filter (Rotella T 15-40W), both fuel filters, breather hose and air filter.

I do a lot of in town driving , but I did go 350 miles on the freeway and got 22.5 mpg.

Hoping to get 25+ mpg,

Hugh
Timing chain stretch would be the first thing you would want to check for performance issues.
Q on timing chain stretch...
617 '05' Camshaft Specifications:
http://www.peachparts.com/shopforum/showthread.php?t=96572
W123 Timing Chain Stretch
http://skinnerbox.steaky.org/Service/W123/Index/617T/05Engine.htm

Then you can move on to checking and cleaning injectors, repack front wheel bearings, adjusting turbo boost, etc....

Danny
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  #14  
Old 10-26-2005, 10:11 AM
t walgamuth's Avatar
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actually

i have found several times that i got better economy in mountains.

after making sure everything is in good tune, the most cost effective thing to change is probably the rear end ratio. you can reap huge benefits there but at the sacrifice of more sluggish takeoff.

tom w
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..I also have a 427 Cobra replica with an aluminum chassis.
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  #15  
Old 10-26-2005, 11:48 AM
Diesel Dad
 
Join Date: Sep 2005
Location: Santa Cruz, CA
Posts: 48
many thanks

NOW, I've got a lot to look into, thanks a bunch.

I'm going to start by looking through the old repair receipts from the previous two owners. First owner (1985-2001) did everything through the dealer where he bought it (Monterey, CA). Second owner (2001-2005) did everything himself.

My car actually pulls kinda hard to the right. Something for me to check or just take it to the alignment shop?


--Hugh

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