An 85 300D should get 22/25 city/highway. I know many people will say thats way too low but I suspect a lot of odometers are off considering they are very prone to slip and fail. Also the amount of fuel put in the tank can vary a bit from when the pump kicks off to topping off the last little bit. Remeber these engines were designed in the mid 70's where gassers were getting 15 mpg. (My 71 250 is getting around 11)

Source for fuel economy.

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Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

..And, according to the EPA, an S-Class is a midsize - compact sedan while the E-Class is a subcompact.

Also, a '93 300SD is rated 20 - 23 city/highway mpg, while the '94 S350 is rated 21 - 28 mpg.
Despite the fact that they are the exact same car with the exact same engine and the exact same equipment they achieved a massive 18% difference for highway travel for the same car?!

My 350SD, rest its soul, was getting mileage on par with my SDL. The 300SDL is rated at 22 - 23 mpg. The 350SD was rated at 22 - 25 mpg. I got concerned when they dropped below 25 mpg. Both averaged 29 mpg in mid-summer in mixed driving (but not overly heavy foot), and about 26 - 27 mpg in the winter.

This winter my SDL dipped below 20 mpg. 18 mpg actually, and I nearly had a stroke. Lost a couple of 6-month old fuel filters along the way.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

Mine's a wagon ('85 300TD), but it's in great shape with very low miles (43K) and has a recent valve adjustment, and it still only averages around 20mpg. Driving up and down highway 5 in california between SF and LA, it averages about 21 MPG at speeds between 70 and 80 MPH. It has the 1985 california emissions system/trap oxidizer, and I run 99.9 biodiesel.

Does anyone get better mileage from their wagons?

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1985 300TD Wagon
Running biodiesel whenever I can get it!

Freeway @80mph I get about 24-25mpg's in my 300SD with a 3.07 diff. At 73mph it goes up to about 26, and if I go 55-60 (state roads) I've seen 29-30.2mpg's Cruise doesn't work, so maybe a bit better with that, but my foot is pretty rock steady...I can go 74mph for hours with no fluctuation.
In the city I get about 22-24 depending how leadfooted I am (usually very)

Our '83 gets around 21-23 city (he's a leadfoot as well) and he generally see's about 27 freeway at 75mph with cruise (his works flawlessly). So overall they're pretty close. We also have different tires and his engine is probably a bit stronger than mine (less blowby). The two SD's can both match each other on the highway at Max Speed (around 114mph for both) I don't think our van could get that high, maybe 105 if its lucky, shakes real bad above 90, so probably not.

Van mpg's: City about 15-17, highway about 22 at 73mph on cruise.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

My '85 300TD gives 20 to 21 MPG on the highway below approx. 70 MPH (loaded). I like to imagine I got 24 MPG with a tail wind once, unloaded at a constant 60 MPH. A dose of RedLine 85+ diesel catalyst or similar cetane booster and a fresh valve lash helps.
Its been my experience that speedometers seem to always read faster than actual as the internal springs age. Anyone claiming they get much more than this esp with pre-85 cars with the 3.07 differential probably have speedo error.
The odometers can be fixed if you replace a little gear that usually cracks. Someone was selling a custom made gear on eBay for a rather steep price considering its just a tiny little piece of plastic. I had a VDO speedometer shop calibrate my speedometer and they replaced the entire odometer with a clean set of wheels for an additional $40 or so (on top of $130 )
It's nice to have a clean, visible odometer because they tend to get dusty and the lower digits can be hard to see esp with the crappy backlighting that MB designed into the instrument cluster. While you have it out you can bypass the dimmer with a shunt to make the lamp full on all the time (what did they think we need that dimmer for? the darned light is too dim even full on so a 5W bulb (Osram 2825) is what some use in place of the 3W bulbs

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

dieseldiehard makes a lot of sense.

if you havent checked your odo against the mile markers and your speedo you are really just kidding yourself.

but if your car is returning 29 mpg (apparently) you may want to continue to live in that world.

i do believe that folks living at higher altitudes will do better with the turbos.

i have had 29 benzes, prob about 7 or 8 turbodiesels.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I agree, you need to verify your odometer on these things. I also have trouble understanding how one could consistently get around 30 mpg, unless you drive very gently. On the other hand, if the mileage is consistently in the very low 20s, I would think you are either driving very hard, doing a lot of stop-and-go, have the ALDA cranked way up, or have some other issue that needs attention (California spec cars may be different). Mine seems to stay in the upper-mid 20s pretty consistently. Maybe there's just a lot of variation between individual cars.

I don't exactly drive the SD "gently". I accelerate at about 2200 rpm and sometimes hold third up to 3K.

I keep the highway speed between 65 and 68 mph.


Then, it's a bunch of little things. It never returned better than 27 mpg until this season.

1) new valves
2) new prechambers
3) 2.88 rear axle
4) 215-70-14 tires
5) 32/34 tire pressure
6) the slightly better aerodynamics of the S class body
7) Perfect IP timing
6) Camshaft timing within 2.5°
7) Perfect valve lash
8) 13.5 psi boost
9) 10 oz. Power Service to 20 gallons fuel


The group of "little things" probably nets me 10% improvement.

And, yes, the odometer is calibrated to the highway markers. The SD has it's own onboard speedometer calibration unit. The error is .05 miles in 25 miles travelled.

I think that's pretty gentle, compared to the way lots of folks drive.

Your mileage sounds just about right based on how you drive and the condition of your car. I don't see how you could do much better with a 617.

I have 3.07 gears, 205 tires, old injectors and pre-chambers, shift closer to 3-3.5K rpm, and cruise at closer to 75-80 mph. My odometer is within about 1-2% based on mile markers. My mileage is more like 24-27 highway, depending on speed, but I don't carefully track it. I was just wondering about the folks who say they are only getting about 20. Either they are driving very hard, or something on their car is less than optimum.

.......yes.......so true........they blow my doors off all the time in a valiant effort to get to the next red light........where they sit.

But, I understand the reason for this. The time spent sitting at the red lights doesn't count in your overall trip time. You get to deduct this time.........

Only if you use that time for a quick nap.

I think that they do. When the light turns green, they sit there for about 3 seconds before they mash that pedal to the firewall..............

We should make them all drive a 240D for a while, to learn about conservation of momentum.

We should make them drive a 240D so that we can observe them suffer a stroke when their blood pressure exceeds 200..........

Maybe we just need a rule that no one's horsepower can be greater than their IQ, that would keep them in a 240D.