Hey guys I am getting poor mpg on my '92 300sd. What I noticed is when sitting at a stop light and taking off, there is a big cloud of smoke. I smelled the exhaust it smells like diesel. Odo works, tranny shifts ok, im thinking it may need a diesel purge done to it. Anything else I can check?

Before diagnosis starts what is your definition of "poor mpg"? Note that Craigslist/ebay claims are pure fantasy and even some claims here are to be polite somewhat inflated due to poor measurement methods.

The cloud could be a problem but it may not be related to the mileage.

Is this a change over the mileage the car used to get, and the smoke a new event?

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On some nights I still believe that a car with the fuel gauge on empty can run about fifty more miles if you have the right music very loud on the radio. - HST

1983 300SD - 305000
1984 Toyota Landcruiser - 190000
1994 GMC Jimmy - 203000

https://media.giphy.com/media/X3nnss8PAj5aU/giphy.gif

How many miles on your 3.5l? Is the engine original?

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

A "diesel purge" will do nothing, you have a problem that needs to be fixed.

Seriously dirty air filter and plugged exhaust come first to my mind.

What color is the smoke?

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

I estimate I am getting about 14-15 in the city. I don't do much highway driving so I don't know highway mpgs. I got a full tank of diesel and I only got 94 miles since fill up and it's almost at the 3/4 mark. Thanks for your reply. I only had the car for a year but I know the mpg isn't right. What is the proper mpg this car should get?

I had the car for a year and am slowly working on fixing the items it needs corrected. This is how it's been since i've owned it.

Almost 205k don't know if it's original or not. It runs good though.

The smoke is whitesh blue, im sure people love it when they are behind me. It's kinda embarrasing.

Impending doom of bent rods here?

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

Yep, blue smoke from a 3.5L =

What's the oil consumption?

14-15 mpg city isn't right if you're measuring properly (odo calibrated, correct size tires, etc.). I'd expect 20 mpg city. I was doing better than 20 mpg city with a couple of bent rods so I don't think poor mpg is an indicator. Oil consumption is but you can be burning oil in the turbo or leaking from any number of places.

Sixto
87 300D

Ya. Watch your oil level closely. If it goes down do a quick check to be sure it's not the turbo, and if that checks out it's probably time to look into cylinder sleeves....

-Jason

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.