240D Mileage... - Page 3 - PeachParts Mercedes-Benz Forum

Graminal95 · #31 10-03-2008, 01:35 PM

Before and after my turbo addition I was seeing 28mpg worst and 37mpg best with an average of 31mpg over 6000+ miles driving all over the US. So you should be getting better mpg but its true you have to average over a few tanks and trips using the amount you put in the tank during each filling. I always add extra fuel after the pump shuts off to a ~ level on the filler tube, that way there is less deviation on the amount in the tank when full.

rs899 · #32 10-03-2008, 02:15 PM

Yup, me too. I fill right up to just below the rim when I am checking mileage, get the number off the odo ,adjust for tire size (which CAN be significant) divide miles by gals. Result- 35. SOP.

carusle · #33 10-03-2008, 09:57 PM

I get over 30 on highway, I hope you are using the pump gallons. My tank will not hold 17 gal.

jaschanks · #34 10-04-2008, 05:21 AM

My 240d auto gets 28-28.5. Mostly highway and driving like my mother. Was hoping for better but engine has ALOT of blowby judging by the oil cap test. Blows it right off. Oh well....

t walgamuth · #35 10-04-2008, 07:22 AM

I'm voting for calculating error, fuel measuring error or odometer error....

or all of the above.

curtludwig · #36 10-04-2008, 09:31 AM

Quote:

Originally Posted by rs899

Haven't checked it in awhile but since I have been running the 240D stick exclusively while my Rabbit is waiting for brakes I checked mileage today.

No surprise (to me) - 35MPG. But... that's at almost a constant 50-55 commute , little stop and go and flat-as-pee-on-a-plate Florida terrain. So it is possible to get really great mileage on these if you have the proper conditions .

Rick

Rick that really is outstanding, very much the high-end of 240D economy. Of course every car on eBay is getting 35-40mpg!

curtludwig · #37 10-04-2008, 09:41 AM

Depends on how fast you're going... The force required to move your car increases geometricly by the square of speed, so 2x the speed requires 3x the force to move the car. Higher speeds will require more fuel per mile.
In my testing there was a sweet spot right around 65mph (probably more like 62 but whatever) after which fuel economy fell quickly. Holding the engine at the rev limiter (86mph IIRC) resulted in a horrible drop in fuel economy plus an increase in oil use.
Rick's post and his statement of 50-55mph on flat terrain makes perfect sense. The terrain here in MA isn't flat (especially where I live) and I drive a bit faster thus my 28mpg average.

My method is to fill until the pump shuts off and to always use the same pump. I keep the receipt from the pump (I always pay with a credit card at the pump) and write the mileage on the receipt. The receipt goes in a binder clip with the other receipts in the console. Occasionally I write the receipt information in my little book which I occasionally bring into the house and transcribe into the computer. The spreadsheet keeps track of everything for me. I've been doing that method for ~70,000 miles on my 190D. Once my 240D gets back on the road I'll do the same thing.

As for odometer slip... I doubt it. Based on what I've seen fixing the blasted things once it starts to slip at all its most likely to just quit. I don't think its going to "be just a bit off". Its a metal wheel on a metal shaft, once they slip a little they'll rapidly polish each other and slip completely. Its not that great a design really, the metal wheel should have a flat spot matched on the shaft...

-Curt

Quote:

Originally Posted by jaschanks

My 240d auto gets 28-28.5. Mostly highway and driving like my mother. Was hoping for better but engine has ALOT of blowby judging by the oil cap test. Blows it right off. Oh well....

nickofoxford · #38 03-20-2009, 11:54 AM

Hey guys, been a while since I poked around this thread. I have my bike odometer set up on the back tire and have it callibrated to the tire size (tire under load). It works great, now I have an odometer acurate to .1 miles. This weekend im going to get a beaker or something as a "fuel tank" and run it on that for 30-40 miles or so and try to get a very accurate reading on mileage.

I spend this week at my vo-tech shool making an LCD readout that will divide information from the odometer and somehow find a way to measure fuel consumption at the engine..

fruitcakesa · #39 03-20-2009, 01:20 PM

Regular 50 mph local highway cruising gets me 28 mpg in the 82 auto
but local stop and go is 20-22 mpg only.
Then again, here in Vermont, everything is local with lots of hills and curves and very little flat and level
I have not run the 81 stick yet to compare.

johnbonds · #40 03-20-2009, 04:20 PM

For what it's worth, I have owned my '82 240D 4sp since 1986 and put about 150k on the car (had 56k when I bought it). I have averaged 30mpg + or - on every tank. Sometime back, I had an algae problem and couldn't get to the reserve part of the tank (ran out of fuel and could only get 14gal in it thereafter). So I refuel at 300miles on the odo. Takes 10gal plus or minus, usually minus. It's a daily driver around town--up to 60 on the bridge to Charleston, up to 70 on the interstate, otherwise 35-40mph. It really doesn't seem to make much difference whether I'm on the road at higher speeds or not--still 30mpg plus or minus. I commuted in it when I went to grad school in Columbia (100miles each way) in the mid-90s.

I keep the tires at 32#, as lower pressures affect mileage. I change fuel filters at every third oil change. Valve adjusted every 30k, new timing chain at 190k. You might want to check the butterfly valve in the air intake (under the air cleaner). At one point mine stuck in the nearly closed condition. Cut mileage and power noticably. WD40 and movement fixed the problem.

John Bonds
Charleston '82 240D 4sp daily driver

WD8CDH · #41 03-23-2009, 07:58 AM

Quote:

Originally Posted by nickofoxford

I have my bike odometer set up on the back tire and have it callibrated to the tire size (tire under load). It works great, now I have an odometer acurate to .1 miles.

If you really want to be accurate, you need to calibrate to effective rolling diameter, not static loaded radius. Since a tire tread doesn't stretch much, inflation makes little change in the circumference even as the center of the wheel lowers. It's like a tank tread, the outer tread still only makes one revolution per wheel revolution.

Look up your particular tire model at the manufacturers web site. It will give the "revolutions per mile" which is much more accurate than measuring the tire under load.

By the way, under load, it's the diameter of the belt layer, not the tread surface that dominates the effective revolutions per mile.

IndianaJo · #42 03-23-2009, 04:01 PM

My way to calibrate the odometer is drive in the country on the interstate, look at the odometer at a milepost, look again 10 mileposts later. Do it again, mileposts are sometimes moved by construction. 2 answers the same, you have the calibration. Don't trust mileposts in the city, they get moved around a lot. I check milage by filling up, writing down milage, filling up again, writing down milage, dividing miles traveled by gallons. My 240d manual got 26 mpg suburban right after motor overhaul, 28 after I changed the injectors (at 229000 mi), now down to 22 mpg after 6000 miles probably because the P.O didn't have the cylinder liners changed or bored cylindrical at overhaul. (Could be valve lash, on my to do list). If brakes are dragging, the wheel will be warm to touch after 15-20 miles. My front brakes drag, a new everything has not helped. Poor combustion causes blue smoke and soot, proper engines are pretty clean warm.

leathermang · #43 03-23-2009, 04:23 PM

My 1980 240d manual trans has always gotten 24 mpg... I suspect the average old 240 gets 28 on average. I think the FSM has what MB expects listed.