What do ya know.....here's an '85 SD with those wheels:

Hello - I can now attest that a 300d (1985 2.88 diff. 4spd manual ) will get over 35 mpg!!!! I have a 1985 300 d with about 160K on the clock - I just got it out of paint and put a kit in the turbo, adjusted valves, new glow plugs, new bosio injectors, installed a boost and egt Gage and turned the boost up to 13 lbs, backed the alda out about 2 turns along with all new filters and fluids. I checked my speedometer against 2 gps systems and it was spot on I just drove 303.5 miles some freeway 65 and 70 - some 2 lane 55 - 60 - 2 trips over the coast range (1200 ft elevation. and up 101 thru small towns - speeds down to as low as 25 and as fast as 55-60 lots of speed traps at the coast (ocean people thrive an valley money). stated off filled up to the neck and filled it the same 303.5 miles later and it took 8.5 gallons - thats 35.7 miles per gallon - best of luck to every one !! I am more than happy with my old Benzo!! jeff edwards

Jeff, Welcome to the Forum.

That is great mileage on your 300D, but this thread is about the 300SD fuel mileage.

I also did the 4-spd swap on my 85 300D. picked up 3 MPG from what ever I was getting with the auto trans.
Everything stock and nothing tweaked.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Go for the 2.47 diff., my 300sd picked up 7 mpg at 80mph. Its something like 32 miles per gallon now and i dont notice it being any slower. Plus it keeps the car in the ideal toque range.

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84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800

That's according to whether you're driving it or selling. If you're driving it they will get between 21ish and 30ish according to how fast you drive and how many red lights, kids and puppies you stop for.

If you're an honest seller that's what you tell a prospective buyer.

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84 300SD
85 380SE
83 528e
95 318ic

If you're getting 35mpg why would you ever sell? I sure as hell ain't selling.

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CENSORED due to not family friendly words

manual transmission + low ratio diff = better mpg, and with the diesels having their peak torque down lower in the rev range, it saves a lot of fuel that would otherwise be used to overcome the friction of the engine and drivetrain.

i had 3.46 diff + 5 speed transmission in w123, 1000km for 75 litres of fuel which is 31.3mpg for you USA folks, if i had a lower ratio diff, i could probably do the trip on 1 tank of fuel :O

I might have a report on an SD with a 307 differential in a few months. I'm not expecting 35mpg.

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84 300SD
85 380SE
83 528e
95 318ic

Is it manual or Auto transmission ?

the auto slushbox transmission is very inefficient, in fact you're probably wasting away 20% of your fuel usage just to how inefficient the auto boxes of that era are.

I did 1000km trip in it between Brisbane and Sydney, i had the stock 4 speed auto transmission, it used about 110Litres of fuel

I did the same trip in the same car a year later, but with a manual transmission and used about 70 to 80 litres of fuel

I just wish i had a lower ratio diff, here in Australia, we didn't get the turbo om617 motors, only Naturally aspirated, which all came with 3.46 diff instead of 3.07

If i had the 3.07 diff, i could probably have done the trip on a single tank of fuel ( 600 miles ) Definately could have with the 2.88 diff + manual transmission

You're giving up a lot in acceleration and normal low speed driving on hills or with a loaded car. I had a 2.65/5spd for a long time on my w124 5spd and the low revs were great on the freeway but on the flip side if I loaded it up with passengers and cranked up the AC it was almost undrivable in stop and go traffic or on hills. Evetually I swapped the 2.65 -> 3.07 and it's much easier and quicker in those situation. Ideally I would have a 6spd with a 0.84 5th and a 0.70 6th gear. That would be the best of both worlds.

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CENSORED due to not family friendly words

I think a ratio of around 3 is a sweet spot.

2.88 is a bit low, but 3.46 is too high.

I have a 3.06 from an unknown chasis car that i'm figuring out to put into my w123. It should knock down the rpm's by 17%

which will keep fuel economy good and not hurt the driving experience as the rpm's will be in peak torque range and coupled to the manual gearbox i have a bit more power to the wheels than with the auto transmission.

I was going to say to pass whatever it is you're smoking but then I saw the 4 speed manual. That makes perfect sense!

I had the same vehicle for many years and averaged 25mpg regularly. Great car. Shame the 2.88 differential was only on that last model year.

I miss my w123.

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-Typos courtesy of my mobile phone.

My 85 SD regularly achieved 30mpg combined driving...

My 84 with the 3.07 rear gets about 25...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I expected the 3.07 to cause problems around town. My tires are 15" 215 and I believe r75 won't help my fuel consumption either.

I'm just looking for reduced rpm on the highway. Either way I'll check both and mixed driving before I produce a report.

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84 300SD
85 380SE
83 528e
95 318ic

It's a shame that aerodynamics play such a big part in fuel economy. I prefer the older 300d look to the 300sd.

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-Typos courtesy of my mobile phone.