Dear friends:

I have heard and read that some Mercedes 240D (years 1979 - 1981) can get as high as 40+ mpg (highway) even with AUTO transmission while other Mercedes 240D (same years) can only get about ~ 24-27 mpg (high way) even with MANUAL or AUTO transmission. Why is there such a large discrepancy in mpg?

It also seems that 240D can come with either 4 or 5 cylinders. Why the model name does not have some extra letter to differentiate between 4 and 5 cylinder ones?

In your treasured opinions, what parts should be recommended to be replaced in a 1981 Mercedes 240D (4 cylinders and manual transmission) when it reaches about 230K miles?

Thank you very much for all your precious help.

Best regards,

Eric

Regarding your question about MPG, I believe that a lot of the numbers you see reported are either from very lucky individuals with exceptional cars, faulty odometers, or myth.

There was a thread a while ago on the Diesel Board about MPG, and GregS gave out a link to www.fueleconomy.gov. I checked to see what kind of MPG my 300TD-T was supposed to be getting, and my car is pretty much on the mark. BUT, if you compare my mileage to others around here, I'm missing out on 7-8 miles a gallon...

By the way, the fueleconomy website only goes back to 1985, so it may not be of any value to you.

I think driving conditions (city vs. fwy, hilly vs. flat terrain) constitute most of the descrepancies you're hearing regarding mileage. Obviously the state of tune is a huge factor as well. Another thing I just thought of w/the manuals (as I just recently purchased one), is driving style - i.e. how much you rev the engine before shifting.

You should definitely be getting 30+ freeway with a 240D. The 40+ figure does seem pretty optimistic, but a friend's old W115 220D ran like a top and got 38mpg on freeway jaunts.

The 240D is only for the 4-cylinder. It is the 300D that is the 5-cylinder motor - a bit more power, but pooer mileage (expect around 26-29 freeway depending on the above mentioned factors).

Regards,
- Ryan

__________________
'95 E420 - 'Shadowfax' 138kmi.
'92 Volvo 740Turbo Bard 193kmi
'74 240D - 'Ol' Green' 4spd Manual 104kmi. (sold )
'77 300D - 'Red' 223kmi (sold)
'75 240D - 'Bianca the Blue Bomber' (sold)

One other thing to remember, is that with a diesel, the torque is available is much higher than with a gasoline engine. Having said that, by giving up some off the line performance, you can gain gas mileage by running larger tires.

As an example, by putting the largest tires on an 83 300D that would fit in the wheel wells, the "indicated" gas mileage (miles travelled on the odometer/gallon used) didn't change. What changed was the actual number of miles travelled however, which increased. On a test on the freeway, when the odometer said 65 the car was doing 80. That is a 23% increase, so if you were getting 28mpg before, you'd be getting 34mpg after.

Obviously there are other factors (like the fact that acceleration was slower) but on the 300D I could drive as fast as I wanted to, which was probably faster than I should have been going in most cases. Having an automatic really lessened the effects of the larger tires (simply because off of the line the torque converter can slip allowing you to run at a higher rpm to accelerate as fast as you'd like), but I had slightly larger than stock tires on my 77 240D and I couldn't tell the difference.

You can also change this a good amount by changing tire pressure or tire brand. In my experience Michelins will give you more mpg. There may be another brand that has less rolling resistance, so if this concerns you, look around. I lost 2mpg (out of 21 that I started with) on an SUV changing from Michelins to Generals of the same size.

Anywho, I was getting an easy 30+ mpg on my 77 240D. I never paid attention to the 81 240D, and on the 83 300D (turbo) I was around 30 on the highway.

-Tad

Little did I know . . . I gave away my '80 240D when it reached 300,000 miles because I thought the engine was about to go. I rue the day! Anyway, for the 200,000+ miles I drove it, I averaged between 24MPG and 29MPG. Mostly freeway driving, but some pretty steep hills along the way. Driving a 240, one really learns to look ahead and plan accordingly.

I agree. I think that everyone should have to drive a car with the power/weight ratio of a 240D just to appreciate how to better deal with the other cars around them. It really does make you plan, and probably makes for a better driver as well.


-Tad

I heard it said many years ago that the biggest lies are related to income tax and fuel mileage.

I am a total nut when it comes to calculating and recording my fuel mileage. I keep a notebook in the glovebox on all my cars in which I keep chronological records including every fuel up. A fuel up entry consists of date, odometer reading, trip odometer reading(which I reset at every fuel up, gallons added and calculated MPG.

Being the anally retentive car nut that I am, I have had many, MANY conversations about fuel mileage over the years. It always amazes me that so many grown people that have obviously made it through fourth grade mathematics class, which is all the math skill you need, don't know how to calculate fuel mileage.

Many people will fill it up, drive a certain number of miles and look at the fuel gauge and make some wild calculation like, "I used a 1/2 tank and went 300 miles, so I got about 60 MPG" or some stupid thing.

To get to your answer, My 240D was operated about 90% on the highway and it averaged about 31.5 MPG over its life. With such a small amount of horsepower, the a/c would pull it down to about 30.5 in the Summer, and it would get around 32 or 32.5 in the Winter.

Have a great day,

Thank you all very much for your information.

I have some other questions:

1) How much horse-power does a 4-cylinder 240D engine have?

2) Is it true a 240D with auto transmission is AWEFULLY weak while a similar one with manual transmission is much more powerful?

Best regards,

Eric

1. OM616.912 engine from 02/76 to 02/79 have 65 horsepower;
from 02/79 to 11/85 have 72 horsepower

2. The automatic and standard transmission 240D's have the same horsepower output. However, with an automatic transmission, the 240 is as lazy as an ol' coon dog on a September afternoon. It just doesn't move. The perfect automobile for a teenage daughter . . . safe and slow. If you really don't care what time you get there, and don't like manual shifting, an automatic would be fine. If you want to experience the thrill of controlling your motor, the stick is the way to go. When I had my transmission pulled for something or other at 250,000 miles, the mechanic couldn't believe the condition of the clutch. He said it was like brand new. A stick shift also saves brakes. I finally put the second set of front brake pads on my stick shift Ranger at 210,000 miles. Only had to put one set of pads on my 240D in the 200,000+ miles I had it.


A useful site for W123 owners:

http://www.geocities.com/SiliconValley/Pines/6633/w123.html

Kinda spartan but some good tech info available.

I've got a total of about 100,000 miles on 2 240Ds. My average over those 100K miles is 27.6 mpg. A few people might get a little higher--maybe up to 30--but I drive the cars year round and winter fuel consistently lowers the average.

Anybody who says 40 mpg for a 123-model 240D is either unable to calculate averages or lying. I've never seen the 40mpg claim made except in a used-car sales ad.

The auto and manual models have the same power. The manual is usually a little faster because users wind up the engine more. I like the manual model and wouldn't own an auto-trans model (as long as I could find a manny tranny). The early models had 62 hp (through 1979) and the later ones 67 hp.

These are not rocket ships!

Only 65 or 72 HP?

Does a GM Geo Metro engine or Toyota 1.3 L Starlite has more HP than a 240D?

I think 240D engine is not very efficient in terms of energy conversion (chemical to mechanical).

Eric

I'm not sure where those numbers came from, but actually the early one is 62 horsepower and the late one is 67 horsepower.

Comparing HP numbers from a diesel to those of a gas engine is comparing oranges to apples. Diesels make more torque at a lower RPM, so the performance from the diesel engine is greater in comparison than the HP numbers might indicate. That said, they are still SLOW.

I have around 800,000 miles in 123 diesels, but the lack of power in the 240D is manageable if you have a stick. The automatic is so slow that it is only useful for a teenager.

Good luck,

Thanks LarryBible,

It's good to know that diesel engines may have low HP numbers but actually are capable of providing more torque than gasoline engines with higher HP numbers.

Eric

I've been getting 22MPG with every tankful of winterized diesel on my '82 240D. I drive it pretty hard(70-80MPH on the freeway) and I expect to see 25-28MPG when it gets warmer. I don't see the car getting over 30MPG unless I fix the cruise and drive at a steady 55(not likely).

I'm not really too concerned but I'm paying a bit more attention to it at 1.979 per gallon. The 90K service is coming due in about 3500 miles. Does anyone think the valve adjust will make a difference? I also just bought a case of Delvac-1 and from what I read on this site it can make a 1-2MPG difference.

On another note, the trunk reeks of diesel. Is this a gas cap issue? I don't see where anything is leaking.

__________________
2002 500SL(Black/Black)
1992 300SE(Black/Black)
1992 190E 2.3(White/Navy)
1999 VW Jetta TDI(Pearl Green)
1986 SAAB 900 Base 3 door(White)
1983 Porsche 911SC(Chiffon)
1977 VW Scirocco(DiamondSilver)

Only if you're measuring in imperial gallons.

Since you're obviously trying to sell the car, its most likely just a lie. The standard reality+10mpg formula.