Why is my '79 240D doing only 20 miles per gallon?

[rino]

I have read the posts of many claiming 30-35 mpg for the same vehicle...
Where should I begin looking for finding the probable cause for all this waste?

Rino

[POS]

To start, I don't think the 240D gets that good of mileage - my w124 gets 34 hwy and 29-30 combined. Based on my knowledge, I thought the w123 was in the 25mpg range.

Regardless, easiest places to start are with clean filters (all of them) and tire pressure. With only 92k miles and a manual, you should be at the top of the heap.

[Wodnek]

Winterised diesel will drop your milage drasticly, due to the lower btu content in the kerosene portion of the fuel.

[rino]

Originally Posted by POS

To start, I don't think the 240D gets that good of mileage - my w124 gets 34 hwy and 29-30 combined. Based on my knowledge, I thought the w123 was in the 25mpg range.

Regardless, easiest places to start are with clean filters (all of them) and tire pressure. With only 92k miles and a manual, you should be at the top of the heap.

Still, 20 mpg seems too low... I've even been using a product from Performance Products over the past year that is supposed to clean the fueling system and increase fuel mileage. Clean filters... I changed the air filter about a year ago, and it didn't help a bit in this regard. I could change the fuel filter... What other filters are left to look into?

Rino

[pawoSD]

I've only been seeing upper teens lately... around 17-19mpg...its COLD here, so that also means the fuel won't atomize as well going into the engine, thus some is wasted....it also takes energy to heat the engine up from being so cold....with lots of short drives this one can be a significant factor. I usually see a 5-6mpg increase in the summer.

[kerry]

Slow odometer.

[rino]

Originally Posted by Wodnek

Winterised diesel will drop your milage drasticly, due to the lower btu content in the kerosene portion of the fuel.

Would that be something I add myself to the tank (what is the correct proportion?)
I live in Los Angeles and here the climate is mild during the winter... is that something to consider before using winterized diesel? Also, how's that gonna affect performance (will it slow the car down even more?) Wouldn't it be more reasonable to first look into what is causing this poor fuel utilization, if I am to assume that I am getting substantially lower fuel mileage than most other 240D owners?

Rino

[rino]

Originally Posted by kerry edwards

Slow odometer.

Is that really a possibility to consider? I mean, is it something common for cars such as these?
I'll have to find a way to measure how well my odometer is performing, in that case...

Rino

[kerry]

Originally Posted by rino

Is that really a possibility to consider? I mean, is it something common for cars such as these?
I'll have to find a way to measure how well my odometer is performing, in that case...

Rino

MB odometers are notorious for malfunctioning and reading less miles than are travelled because the gears in the odometer spins on the shaft.

[Biodiesel300TD]

You definetly should be getting higher than 20mpg. I get better that that in my wagon, and it weighs several hundred pounds.

I would check your odometer on a trip on the highway to see if it's off and by how much. It still shouldn't cause your milage to be that low, unless your odometer is sticking.

Your air filter could be clogged, depending on how much blow by you have. Open the air cleaner and check it out. When's the last time you changed your fuel filters. I would change them, it's cheap and easy.
You could also have a break or two dragging. Which will really draw down your mpg.

Your driving habits could be the source too. If you take off from lights really fast your mpg will suffer. Where as if you drive like a little old man your mpg will be higher.

[tarbe]

Have you had your vehicle a while and the mileage has dropped, or has it always been this low?

I would check the odo with a GPS if you have/can borrow one.

Also check to see if any brakes (including parking) are dragging.

Get your tires up to near max pressure, or as high as your spine will allow.

If you had an oil analysis done, you could see if you have some fuel dilution which may indicate a leaking injector (don't let 240Joe know you wasted money on an oil analysis though ).

Drive like there is an egg between your foot and the pedals!


Tim

[rino]

Originally Posted by kerry edwards

MB odometers are notorious for malfunctioning and reading less miles than are travelled because the gears in the odometer spins on the shaft.

I see... So that would make a case for even more frequent oil changes than 3K or 5K based on odometer reading (sorry, 240Joe, just pulling your leg a bit in this case )

And how many less miles, on average in these instances, can they read, if that's a plausible question?

Rino

[kerry]

The odometer typically sticks when trying to turn over more than one digit so it will stick when the last digit is moving from '9' to '0'

[stcbenz83]

Originally Posted by POS

To start, I don't think the 240D gets that good of mileage - my w124 gets 34 hwy and 29-30 combined. Based on my knowledge, I thought the w123 was in the 25mpg range.

Regardless, easiest places to start are with clean filters (all of them) and tire pressure. With only 92k miles and a manual, you should be at the top of the heap.

My 240D in the summer gets 27-29 city and up to 33 MPG's on the highway. i do the math every time i fill up. course now

[rino]

Originally Posted by tarbe

Have you had your vehicle a while and the mileage has dropped, or has it always been this low?

I would check the odo with a GPS if you have/can borrow one.

Also check to see if any brakes (including parking) are dragging.

Get your tires up to near max pressure, or as high as your spine will allow.

If you had an oil analysis done, you could see if you have some fuel dilution which may indicate a leaking injector (don't let 240Joe know you wasted money on an oil analysis though ).

Drive like there is an egg between your foot and the pedals!


Tim

Always been this low since buying the car. I'll have to check brakes, thanks. Tires are already maximally inflated. Oil analysis, is another option to explore... as is checking the odo... I drive like "a little old man."

Thanks,
Rino