I have a 1984 300SD. I get 27/28 mpg in the 'hood (We have a lot of hills). It does a little better on the highway. The 126 chassis (300SD) was made for the autobaun. It would also be a very safe car for your daughter to commute to school. (4 wheel disc brakes, excellent handeling, solid as a tank) Pick either the 5 or 6 cylinder 300, avoid the 350SD 6 cylinder (problem engine). Highly recomended car.

gsxr:

Good to see a friendly face over here. See ya on the peach forum.

x2. both on how to obtain accurate MPG and MPG for W126 S-class diesel through 1985; my '83 SD gets an average of 25.7 MPG which corroborates original EPA window sticker fuel economy estimate.

Is that just Boise area or all around? I'm pretty sure Ada county is the only one with emissions testing. They could be giving you the leftovers from OR and WA as well, I know both of those use oxygenated fuels.

I read a Popular Mechanics article from the 80's about the SD.They got 23-34 mpg.The German EPA was at Autobahn speeds.Back then Automakers did not lie about mpgs.Hell I get better mileage than a Chevy Aveo.

I see you put the om617 in a ford pu. What trans did you use?,stock benz or adapt to something else. What kind of fuel mileage with this rig?

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I saw in another blog that you have pumped the boost up alot. Have you intercooled?, is your turbo stock?, How did it affect your fuel mileage? Does the turbo spool up sooner? Thanks in advance, sorry for all the questions, I am new to the benz and am looking to wake mine up a little without hurting the motor or shooting myself in the foot on mileage

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I saw in another blog that you have pumped the boost up alot. Have you intercooled?, is your turbo stock?, How did it affect your fuel mileage? Does the turbo spool up sooner? Thanks in advance, sorry for all the questions, I am new to the benz and am looking to wake mine up a little without hurting the motor or shooting myself in the foot on mileage[/QUOTE]

None of my mods hurt mileage.The highest I got at 80mph average,was with 25% used motor oil mixed with diesel.I quit using it,because exhaust stinks.25% waste veg oil,will get me 34 hwy.

It's still a work in progress, I'm going with a Mazda M5R2 from a late 80s F150, in the smallblock pattern, using the Ford 300-6 flywheel and starter. The much larger flywheel should allow it to crank easier as well as eliminate any vibration issues.

Hi 4x4 thanks for the update. There is a guy I have been talking to that used the same set up in an s10. He said the ford flywheel had the same bolt circle with one hole off a bit. He also used only 6 bolts (I'm not sure I would be ok with only 6), but reports a vibration at cruising speed. His trans locked up in 2nd gear so he is pulling the trans to fix and is planning on sending out the flywheel to have it off ballanced to match the benz flywheel. I know on my flywheel it has alot of drill holes to lighten it on 2 thirds of it. Makes sense due to the 5th cylinder. Make sure you mark the benz flywheel to tdc before you remove. Keep us posted on your progress!

Great Thread
 

Great posts and experiences shared by several posters here.
Thank you.:ty:
I know this thread is going on three years, but given the current situation it is becoming more relevant again, at least for me.

I have a '78 300CD with the non-turbo i5 I guess iron block.
What can I do to get my low twenties(mpg) up a little ? :nope:
Unfortunately, it has some 200k maybe more miles, but fires right up, even in cold weather, so compression is good.
Does it help to put newer or thicker oil in it ?

The auto tranny slips from 2-3 and 3-4, but I don't think once in gear, maybe can I adjust something, tighten that up ? :clean:

Does the valve adjustment hugely affect the mpg or only a little ? :rolleyes2:

Maybe new filters all around ?

Shorter differential ? :humm:

Bigger tires ?

I would be thankful for any suggestions or reassurrance of some of the above mentioned items..... :s:

Thanks to All

Alex