Sounds like you're running way too rich.
When the engine is cold, pump the gas a couple of times without starting it, then pull the lid off of the air cleaner housing to see if the chokes have closed. Those will be the movable flaps you will see on top of each carburetor. Then start it up and after it's warmed up, see if the chokes are fully opened. If the chokes are fully opened after warmup, I recommend you check the dwell and timing - points may have worn, causing retarded timing and poor mileage. You may still need to lean out the idle mixture. If the chokes aren't closing properly when cold, a leaner idle mixture will make cold-starting more difficult, but then you'll need to repair the chokes, not fatten up the carb mixture to compensate. Also, is the engine not warming up, the reason you need to replace the thermostat? That will also contribute to poor mileage.

Happy Motoring, Mark

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DrDKW

sorry, for not clearing up the thermostat issue. I'm replacing it because the engine isn't getting cooled off. I think the spring or some part of the thermostat has worn away. Once again I don't know how old it is. I didn't notice this untill running it pretty hard on the interstate during a pretty hot day. I'll check the chokes Saturday or Sunday. And i do use the method of pumping the gas pedal once or twice before starting, I've noticed it has dramatically helped.
Just one question not related to all this... that has been driving me crazy, what is the small, black, round pedal for on the far lower left. It can't be for the clutch, since I have an automatic. It can't bethe parking brake since I have that pull lever under the steering wheel, so what is it?

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'77 300D 387,000 Miles . . .

'69 280S (SOLD)

'79 300CD (SOLD)

It's your windshield washer pump. You tap it (it's a pressure based system) and you get a squirt of windshield washer fluid... plus, the wipers should activate.

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Joshua

'71 250 - daily driver

Michael, 10-11mpg is way low for your car. You should be in the mid-teens city, higher teens to maybe even 20 for full highway. I'd devote your attention to getting this one to run right before turning it toward anything else.

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Craig Bethune

'97 SL500, 40th anniversary edition

'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)


SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)

Alright "cbdo", it makes sence to atleast try to improve the setup of the carbs. before allowing such a beautiful car go. But, i'll have to wait since my knowledge about carberators is light. I'll fins someone who knows more, maybe this week, and maybe get the MPG a bit higher, since 10-11 is rediculous. Especially now that gas in Los Angeles is atleat $2.10 for the lowest grade. I've seen the lowest grade as high as $2.27! I'll keep you guys posted with the progress.

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'77 300D 387,000 Miles . . .

'69 280S (SOLD)

'79 300CD (SOLD)

Michael,
That car should be running on premium fuel. If someone de-tuned it (retarded spark timing) to run on regular, that could be part of your problem. If you re-time it, you'll need to decide if the increase in gas mileage is worth the extra cost of premium.

Happy Motoring, Mark

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DrDKW

The Ponton was the first readily available diesel stateside from MB. You had the 180D(x) and 190D(x) models (mine is a 190Db). I wouldn't have one for a daily driver. They are too slow, ESPECIALLY for LA Kamikaze traffic. Heaters are feeble as blowers were optional in that model. They had manual drum brakes all around, which means you tromp them hard to get an answer back from the car. They are a blast to drive, but not something for daily use in heavy traffic.

Sorry if I made it sound like i was running the car on the lowest available grade of fuel. I've been running it on the mid-grade.

Looking through the autotrader.com, it looks like my chances of finding a 200D (the later fintails) are slim to none, especially around my area.

Since the pontons arn't recommanded by you guys as daily drivers, i'll stay away from them, for now.

If the poor milage continues, I'm guessing it would be best to sell the '69 280S. Maybe I'll get a w123 300D Turbo, and save up my money until I have the luxury of owning W108 again.

Well, I sure learned a lesson from all this, and am still learning the leason.

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'77 300D 387,000 Miles . . .

'69 280S (SOLD)

'79 300CD (SOLD)

I just saw this post also -- this car should get much better mpg than this -- you should get close to 20.

make sure that carb heaters on the exhaust man arter closed - they can stick open.

also on both carbs you will find electric chokes -- make sure that are not sticling closed.

both of the items will cause the mpg to go up.

i'll have the mechanic check, when I hopfully get the brakes done.

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'77 300D 387,000 Miles . . .

'69 280S (SOLD)

'79 300CD (SOLD)