I get about 27 mpg with my 84 SD, the window sticker says 27. The 87 SDL does better on highway, i get almost 29 mpg.

Ed, 38mpg is quite good for that car. If you have a 5-speed, it can get better if everything is perfect (40-42 tops). If that's an automatic though, 38mpg is *fantastic*. The timing chain never requires tightening, it has an automatic tensioner. It requires replacement when stretch equals or exceeds 4 degrees. It's easy to check with the valve cover removed. The procedure is in the factory service manual (which you really need for any serious work on the car).

Wolfie, the 1985 300D had a LOT of differences compared to the older models. The rear end ratio was one of many changes. I agree that the gearing is too low on the older ones. My '84 never gets over 24-25mpg regardless of what I do to it. But they are capable of 28-30mpg when everything is factory new, and I know of some with 200k+ that still get 28-30mpg. Mine was worse when I bougt it (19-20mpg) and I managed to get it to mid 20's through lots of little things. But I've given up trying to get any more out of it - I'll just replace the car with a 190D or newer W124 chassis, as I'm not really fond of the 123 (but that's a separate discussion).

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Dave
Boise, ID
Check out my website photos, documents, and movies!

If I could see 28 on the highway I'd never complain for all the power and the size of the car. That would be 10mpg less than the wors I've ever seen from my VW's. I could swallow that.
I have yet to adjust the valves, replace the injectors and do the timing chain, all are I'm sure do, even though it runs and starts perfectly fine. Perhaps that will help a bit.

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

I just did a roadtrip of 4,150 miles in an 84 300d and averaged 24.9 mpg.

The car needs the valves adjusted, half of the trip was in cold country and crossing mountain passes, I always worked off the top half of the fuel tank, carried 5 extra gallons in the trunk along with four extra tires, survival gear (75 lbs) and misc tools and supplies (100 lbs).

I'm definately pleased and I hope to get the MPG up with some TLC and less of a load!

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1983 300td 240k (down with bad tranny)
1984 300d 222k (daily driver) "Olive"
1997 GMC K2500 105k (sled dog limo)

"The scenery in ANWR is as spectacular as the Grand Canyon and the wildlife is more impressive."

Has anyone disconnected the A/C compressor belt to squeak another mpg or two out of their 300d?

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1983 300td 240k (down with bad tranny)
1984 300d 222k (daily driver) "Olive"
1997 GMC K2500 105k (sled dog limo)

"The scenery in ANWR is as spectacular as the Grand Canyon and the wildlife is more impressive."

The A/C shouldn't be running with the "EC" pushbutton pressed. Removing the belt won't gain you anything, the clutch lets it freewheel when not in use. You'd see more gain just raising your tire pressure, or some other minor change, than you'd ever get by yanking the AC belt!

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Dave
Boise, ID
Check out my website photos, documents, and movies!

4 extra tires? I thought I was paranoid..

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

It was an LA car! They've never heard of M+S tires! I had new studs put on in Missoula and the summer tires went into the trunk. I only went with one spare which is unusually "ill-prepared" for me !

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1983 300td 240k (down with bad tranny)
1984 300d 222k (daily driver) "Olive"
1997 GMC K2500 105k (sled dog limo)

"The scenery in ANWR is as spectacular as the Grand Canyon and the wildlife is more impressive."

I'm only getting 20 mpg in my '84. I need some new tires, wonder if that will help at all.

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RT


1984 300D---Sold
1995 E420 - 106K - Brilliant Silver Metallic/Orion Gray --- Sold
1984 300SD - 151K Manganese Brown Metallic/Mostly Black --- Sold
1982 240D - 79K - Manila Beige/Palomino---Sold

1stimer

I wouldn't think new tires would improve mpg at all and could only reduce it. Mud and Snow tires (studded especially) reduce mpg--the less aggressive the tread the quieter and more fuel efficient they should be. Tire width and height can affect mpg but I'm not sure how much of a difference it would be in the range of tires a person would put on a car like this.

I was getting 20-22 mpg for the first 1,000 miles of my trip, then I switched to 5w 30 synthetic motor oil and put new, very agressive snow tires on it. By the end of the trip I was getting as high as 26.5 mpg even with snow tires and cold temps. I used a fuel injector cleaner in every tank of fuel for the whole 4,000 miles so I suspect that the synthetic oil and injector cleaner made a difference.

Good luck!

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1983 300td 240k (down with bad tranny)
1984 300d 222k (daily driver) "Olive"
1997 GMC K2500 105k (sled dog limo)

"The scenery in ANWR is as spectacular as the Grand Canyon and the wildlife is more impressive."

I just added some additive today for the first time, so we'll see how that goes. I'm afraid to switch to synthetic oil, but probably will when I move to Wahington next year.

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RT


1984 300D---Sold
1995 E420 - 106K - Brilliant Silver Metallic/Orion Gray --- Sold
1984 300SD - 151K Manganese Brown Metallic/Mostly Black --- Sold
1982 240D - 79K - Manila Beige/Palomino---Sold

1Timer,

Why would you be afraid to switch to synthetic oil?

Isn't that like being afraid of switching to a higher quality fuel?

P E H

If he has a lot lf leaks, or slightly worn valve stem seals, that's plenty reason to be afraid.

This is pretty common knowledge, I thought?

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One more Radar Lover gone...
1982 VW Caddy diesel 406K 1.9L AAZ
1994 E320 195K

I get MPG's in the low 20's with my '85 300D CA model and that is combined driving with a very heavy foot. I still have to original sticker as well (curiously two of them) and it states ONLY 21 and 22 for the EPA ratings.
The worst I've gotten was 20 mpg's and 25 as the best. This is a car with over 200K miles on it. Even the previous owner said he got around 20 mpg's from my car. If I plan on keeping this car for a long time, I'm thinking of getting rid of the oxidation catalyst and converting it to a federal intake/exhaust set up as I would imagine the CA set up robs fuel economy in addition to HP.
Another interesting thing I've read from a 1982 Consumer Guide book is that in 1982, the 4-speed automatic replaced the 3-speed automatic as standard equipment in the 300's. They also switched to a 3.07 rear axle. So I guess everything before 1982 that had automatics were 3-speeds. Is this correct?

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DJ


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

I've kept good records of mine over the past 18 months since I bought it. I consistently gets 26-28 in the warmer months. If the A/C is on most of the time, it will see the 26 number typically. On a road trip where the engine does not get shut off for 300 miles or so, it will get up over 28.

Now, in the winter, all bets are off. I falls to 23-25 and stays there until the winter fuel is changed back to the summer fuel.

It has no EGR and larger 215-70-14 tires. The mileage listed is not adjusted. In reality, the vehicle travels 3% farther so the fuel economy would be better by 3%.

The figures are all highway and virtually no city travel. The highway speed is typically 65-70. If the speed of 70 is exceeded for any measureable length of time, the fuel economy will drop a couple of points.