Hey everyone. I recently became the proud new owner of a 1981 240d automatic w/ 138k original miles. Since I got it I have fixed a fuel leak, performed a diesel purge, replaced fuel filters, replaced two faulty glow plugs and adjusted the valves. After all of this and driving between 60-65 mph I am still only getting about 22 mpg. I checked tire pressures to make sure they were all correct and have no other known problems that i believe would cause me to get this kind of mileage. My question is what kind of fuel milege should I be expecting and what else should I check. I would be happy to hit 25 mpg but would like to get closer to 30 mpg if possible. I plan on changing the air filter but it doesn't look too bad and I didn't think it would make that much of a difference. Any feedback/ideas will be much appreciated. I drive about 75 miles a day and want to get the best fuel mileage possible. Thanks, Dane

My 82 auto averages aroungd 25 mpg and my 81 manual about 30 mpg.
Lots of short hops with occasional highway runs.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

check your brakes. verify none of them are sticking.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I definately do not have a brake dragging. Today I tried shutting it down w/ the shut off swtch and the engine and it wouldn't stop it. Most likely a vacuum leak or is there an adjustment on the IP??

you know there is a difference between brakes dragging and a seized caliper right?
not shutting down is most likely a vacuum leak. but there are numerous things it could be. start by verifying you have vacuum going to the switch, then trace the problem from there.

At 65 mph that is out of your economy curve. On my automatic 240D 26mpg @ 50mph is normal 29 on the standard 240D. Your mpg at 60-65mph on a automatic is about the same as mine. Remember to have fun with it. I hope you didn't buy the car with the promise from the seller of 40mpg as seen often.

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1979 240D Caledonia Green/cream gone
1982 240D stick Ivory/Palimino
1999 E300D White/grey

Check injection pump timing but probably not the cause even if retarded a little with a stretched chain. Remove and have the injectors checked. Make sure there is adaquate base pressure in the injection pump.A compression check as well. If you do all the work yourself the expendature is minimal.

All 240s especially should have that injection pump base presssure checked just in case. You will automatically get some increase in milage and power if the pressure is raised to 19 pounds and you drive the same. How much depends on how low the current pressure is. Make no misteak though you will get some better milage component. Do it and tell us. Be accurate.

Ugh yeah, i realize there is a difference. I'm not new to wrenching on vehicles just new to these cars.

I definately wasn't expecting anywhere close to 40 mpg, I realize its no VW TDI. I love driving these cars! I guess I just expected it to do better than my POS 300D, not that my 240D is a peach.

Low 20s is all you should expect out of that car in city driving with the A/C on. It's not like it has a turbo to help it with it's MPG.

My 1978 240D automatic averages 26.5 mpg in city/highway driving. On the highway it usually gets about 30 mpg, but I have to drive 55 in order to do it. When I last drove any length at 65 mph, I recall it averaged around 25 mpg.

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'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k

That's about what my 83 auto does too.

90% is highway and i don't run the a/c.(it doesn't work). Just checked this tank and it was better...averaged 24 mpg. Fuel quality could definately be a concern. Going to replace air filter and slow down to 55-60 mph and see where that gets me.

Anyways, I need to know where to install the fluid gauge to check my base fuel pressure.

My 81 240D does pretty well compared to the other ones I see on this thread. I get about 24 around town with AC on. I get about 36 on the highway running about 60-65 mph. I am not sure why my highway MPG is so much better (most folks report about 5-7 MPG improvement versus city driving, mine is 12 MPG better). After I bought car I put new injector nozzles in, maybe this is the difference.

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Treiberg's Collection: 1981 240D, 1985 300SD, 1992 300E, 1997 E300D, 2005 C230K

In my opinion provided your milage figures are verified somehow. The new nozzles are not the reason. They of course do not hurt. Most 240d owners will disbelieve over thirty miles per gallon is possible on the american gallon. If I did not have a higher fuel milage 240d standard example in storage and had not witnessed it myself I would not believe it is possible either.

If I were to drive that car before getting to the bottom of the issue. I may never find it. Since the aquisition of that example it is the reason it has been in storage until I get the time to really go over it. Something has to be different I just do not know what.

In fact a couple of years ago I went mentally searching for the average five mile per gallon overall difference constantly reported on the 616.

No conclusions where arrived at by me. It was instead discovered during the search the seemingly very important factor of the base fuel pressure being present in the injection pump. It really needs to be at about 18-19 pounds especially on the 616. So if your milage is suspect check it properly and adjust it.

. The cost in the small amount of money and effort will in all cases be returned very quickly. I know of no exceptions to this up till now. The more of you that take this on the sooner others will follow.

Just honestly report the differences you find on site will do it. It really is almost something for nothing as far as costs relating to car maintenance go. If you do not want better fuel milage smoother idle hopefully better starting and more power of course just ignore it. At this point it is not subjective but factual in my opinion.

There has not been one case of the fuel pressure being elevated to the maximum permitted presently of 19 pounds not reporting power gains and milage gains. Thats if they drive the car as they were before the correction and do not exceed the 19 pounds injection pump base pressure.

Yet there is still resistance to doing the small amount of work to accomplish this. There are no known risks. It will also teach you more about the fuel system than perhaps you want to know.

The gauge if installed permanently will make the car much more reliable in service. It will indicate falling supply pressures well before a problem is serious. Again once again paying for the small cost in time and money to install one.