240D Mileage... - Page 2 - PeachParts Mercedes-Benz Forum

nickofoxford · #16 10-01-2008, 05:21 PM

Curtludwig,
Thanks for the correction I remember reading that somewhere on here but you seem to know whats right here. I'll take your word for it

.

So fuel filters and vent cap on the to-do list, so I take it the tank vent isn't in the cap, but somewhere else on the tank?

I will work on hooking up a much more accurate odometer I mentioned earlier to get a better MPH reading, I want to make this a science

I'll post pictures as I said earlier for you guys to check out.

That said, who has a good method of knowing where your fuel level is. I have been using the top up to the filler cap method to know where it is full, but is there a way other than dipping the tank to find out how low the fuel is? I don't know if I want to rely on the gauge for that too much. For precisions sake I could just go ahead and hook up to a different fuel tank?

So with the digital odometer and a good way of measuring fuel levels we can start making real measurements

. This way we can narrow down what actually affects fuel mileage, I'd like to contribute this "project" to the forum so if anyone has tips I'd be happy to try it and post the results.

Should make the mythbusters proud to say the least...

chetwesley · #17 10-01-2008, 05:34 PM

The tank vent is a hose that comes off of the tank and is open to allow air in.

nickofoxford · #18 10-01-2008, 05:42 PM

Ok so where is this hose? Im guessing I have to pull the rear window shelf again

chetwesley · #19 10-01-2008, 06:00 PM

Quote:

Originally Posted by nickofoxford

Ok so where is this hose? Im guessing I have to pull the rear window shelf again

I am not sure on the 240d where it is... I haven't poked around mine enough yet. On the 300TD IIRC, it was a third hose coming off the tank (along with the supply and return lines), but that car has the tank on the underside of the vehicle, not behind the seat like in the sedans.

nickofoxford · #20 10-01-2008, 06:17 PM

Oh ok I know what you are talking about, I'll check that out thanks for the tip

.

curtludwig · #21 10-01-2008, 07:01 PM

Ahhh, I forget where the tank vent ends up, its under the car, somewhere in line with the tank, I *think* on the driver's side but I'm not sure. Look for a plastic trumpet sort of thing. If you look a the tank a metal line that isn't a fuel line, the vent comes off the top of the tank, you could follow it to find where it goes.
Theres a check valve kind of thing on the end which gets plugged up. So pull that plastic whatsis off and clean it out with compressed air or WD40 or whatnot.

You'll know your tank vent is plugged because when you remove the tank cap you'll hear a "whoosh" of air going in.

For filling to the same amount just fill until the pump shuts off and always use the same pump, thats gonna be the easiest way to get at least close to the same fill every time. Remember you can't be absolutely sure of your mileage on any one fillup you want to look for trends over thousands of miles.

nickofoxford · #22 10-01-2008, 07:30 PM

Thanks for the advice

I will get on that vent, she seems like she looses power as the tank gets empty so you could very well be right.

94mgm · #23 10-01-2008, 07:42 PM

Suggestions:

Dragging brakes.
IP timing.
underinflated tires.
low compression.
Failing transmission.
you're VERY fat.
Overreading odo.

Stevo · #24 10-01-2008, 08:01 PM

Quote:

Originally Posted by nickofoxford

Thanks for the advice

I will get on that vent, she seems like she looses power as the tank gets empty so you could very well be right.

The vent comes out of the tank alongside the return line, above the driver side half axle, its the larger one, as I remember, follow it from there. Good luck

rs899 · #25 10-03-2008, 08:55 AM

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

75Sv1 · #26 10-03-2008, 09:07 AM

I haven't run my 240D manual tranny much. I'm still trying to bleed the clutch system. Hope to have time on that this weekend. All the suggestion looked good to me. Many of them fairly easy to do. Two I would add are possible grease the front wheel bearings. I'd add the rear too, but I think they are more involved. The other is check to see if your auto trans is slipping. You will get wort gas mileage on country roads, than pure highway driving. I would get 32-35 in my '96 Ford Contour on the highway and probably 24-26 daily commute on country roads. I get about 30 mpg in my '00 Contour SVT on the highway. I hope to get more. I finally got the wheels striahghtend, aligned new bearings etc. and its driving good. Still I'd say probably a 6-8 mpg difference in pure highway and even mostly back road driving.
Tom

Stevo · #27 10-03-2008, 10:34 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

Some might think your numbers are off someplace, or your odo is recording incorrectly but ..."it is possible to get really great mileage with a 240D if you have the proper conditions". I know a couple folks that commute, more or less, with their 240Ds and get that mileage. Many of the roads in this part of the country are 45-50 mph, makes driving almost fun.

rs899 · #28 10-03-2008, 11:09 AM

I'm quite sure I got the fillup/math technique right and I am fairly sure the odo works properly (if anything, they slip don't they?). I am just a pretty gentle driver when I am not pushed and keep the revs down. Not going to win any races with a 240D .

Stevo · #29 10-03-2008, 12:36 PM

a few years ago I sold a manual 240D to a young "neighbor" lady that needed a dependable car for her 50+- mile commute, she asked about the MPG and I told her somewhere around 30, saw her a few weeks later and she was happy to report 36 mpg. I felt kind of silly suggesting she check it again, but she did with the same results, shes a scientist, probably knows more about keeping track of this kind of thing than I do

Anyway its the "perfect" driving conditions plus the car was in top shape.

Bajaman · #30 10-03-2008, 01:13 PM

I don't think anyone mentioned the obvious possibility of not really using 17 gals. In you first statement you said that you were going by the reserve light. The accepted method is to use the amount of fuel you put into the tank, not what you think you got out... In other words fill to the neck, drive, fill to the neck again and use this mileage for your MPG calculation.