So my "new" (208k mile, 85 300D) to me MB is getting around 25mpg around town (very little highway) with a bad thermostat (temp stuck at 60C) and a very clogged air filter, its had a fresh valve adjustment.

So now I've fixed the thermostat and put a new air filter on it, what kind of highway miles should I get? I'm thinking at least 30 as I drive it slowly like an old man 55-60mph.

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Current Rides:

2004 BMW R1150GS Adventure
2005 MB W211 E320 Cdi

30 is not really possible, you'll get closer to 26-27mpg. 25mpg is already very good.

I keep track of every time I fill up. Over the last 8663 miles (almost 2 years - I don't use the car much) it has averaged 27.52 mpg. In the summer it usually is 28-29 and in the winter 26-27. The difference is in the fuel itself rather than the temperature per se (my opinion). I also have an '82 with longer history and its mileage is close the '85 and also goes down in winter.

Agreed. I've tracked mpg on every single fill up on my '84 300D since August (about 20k miles). In the winter, it's anywhere from 21-24. In the summer, it's usually 26-29.

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1984 300D: 275,000 miles (soon to be for sale)

In search of my 1987 300D in anything but white.

These figures are not that different than mine and you guys have twice the HP

I thought some of the 1985 with the 2.88 final drive could get 30 on the freeway if, driven easy. When I had my 300SDs my best ever was 28 and that was on a leisurely trip, mostly on 2 lane highways where I never exceeded 60. That was with 2 people and luggage. Driving at 70 or so, 25 was more typical. In town, my mileage could be as low as 19, because of my lead foot. 240D's are working so much harder that low 20's in town is typical. At sea level I averaged about 25-26 in mixed driving with my 240D.

So, you're actually doing pretty well.

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1979 240D, 4spd manual, Power Sunroof, manual windows, 147k miles, Pastel gray/Black MB Tex.
1991 300D 2.5 - Smokes like it's on Crack!

My 85 usually gets 25-26 ish, my 83 is getting 27-29. I'm suspect of the 83 though.

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