I know there've been lots of discussions regarding this. I always thought my 83 was getting about 28 MPG. If I run the tank down to say about 2 gallons left inside, I routinely calculate out to 32~33 MPG. I know it has to do with hauling a lot less fuel around. So if you get crappy mileage calculations, but routinely fill up say from about a 1/4 tank or so you actually may be getting calculations skewed by weight of the fuel. Since I now have found a reliable diesel station near work I can risk letting the tank run down pretty low. Still haven't let it run to light on conditions because I don't know if the damn thing works or not.
Happy Turkey Day All!!

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1985 300D 197K - Semi-Daily Driver Diesel
1998 Volvo V70 AWD 226K - Daily Driver 2
1998 Volvo S70 140K - Wife's DD
2003 GMC Sonoma ZR2 Option - Rusty Truck
THE BABY 1958 220S Sedan 66K All original, never restored and never will be.

you are thinking of trying to always run with a very empty tank? i wouldnt bother. the weight really doesnt come into effect except when accelerating and stopping. at steady speeds it is the wind resistance that will determine you r fuel economy. the savings will not be measurable in my opinion.
just keep it tuned, clean filters and good fuel, air pressure in tires correct or high and you will be doing all that is worth while for mileage.
besides, you are already getting mileage to kill for.

happy t day.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Not to mention the risk of running out of fuel and the condensation (esp. in winter!) that you would get from running empty all the time...changing fuel filters and repriming in winter=BRRRRRR!!!

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1982 300DT 190K (Diesel Purge + synthetic oil=smoothness at last!!!)
2004 Ford E-350 6.0 L PSD 227K
2006 Dodge Ram 3500 SRW HO Cummins 4X4 48RE 42K (brute force tow vehicle)
2005 Scion xB wife's rolling pop can
1993 GMC Sierra C3500 6.2 142K

I try to keep my tank above 1/4 just to avoid whatever crud is in the bottom of the tank. 20 gallons of fuel only weighs about 150 pounds (about 4% of the car's weight). I doubt that's enough difference to increase mileage by 4-5 mpg.

Whether your tank is full or empty, you're always sucking from the bottom.
300CD '84

I would just prefer to avoid using the concentrated stuff at the bottom of the tank (probably including water) all once. I have run mine down to the reserve light a few times, but I try to avoid it. Also, I don't know how clogged my screen is. Some day I'll get motivated, clean the screen and drain the bottom of the tank. I doubt it's ever been done in 23 years.

I found out once that my reserve light actually works... and comes on when the tank is... EMPTY!

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

So we have someone strategizing fillup intervals in order to improve his mileage. You have got to be kidding! Shopping for fuel at a couple of pennies less per gallon is silly, but the strategized interval thing is just bizarre.

Next we are talking about never letting the tank drop below 1/4 because somehow we think that the fuel sits in layers. Hello! Just what do we think the fuel is doing as it enters the tank on fillups. It is sloshing around becoming one homogenous pool of fuel. When the car is moving, left to right, start, stop the fuel continues to mix.

Steve

Last time I checked water was heavier than oil. If you have any water in your tank, it will be at the bottom. In addition, condensation will have more opportunity to form in a tank that is left near empty. Also, the design of the screen is such that the full surface area is not available when the tank is near empty. If your screen is partially clogged, you may see some fuel starvation at low tank levels. I just don't believe there is any good reason to try to use the last few drops of fuel in the tank.

Braverichard,
I think the low fuel light is supposed to come on momentarily when the car is first started just to show if the bulb is working. It comes on while driving at the bottom travel of the fuel sender. There should still be a couple of gallons left at that point & as we know, the Benz will run out when the tank is pretty much dry. In the past while rushing to work, I've driven at least 50 miles with the light on. Paul. central FL
300CD '84 290,000

I fill right up to the neck, then drive until the reserve light is on. I've actually run it down to the point that I was able to put 20 gallons in it - rated capacity is 20.3

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Tjohn

82 300 SD
77 450 SL (gone)

If you fill it to the neck the capacity is more likely around 22ish gallons. I fill mine to the neck also, and have fit 19.7 gallons in it before....when I ran it down real far....


As for MPG, with a combination of: 275 miles at 80-90mph, then about 80 miles of city driving, I averaged 22.8mpg on my last fillup. Not bad!!!

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Okay I drove my 300SD until the eninge was coughing/sputtering around corners and I still haven't ever put over 18 in my tank.

Is my tank collapsed?

I am aware of how the reserve light functions. I'm just saying that mine doesn't work well, which was why it never came on until the tank was empty and the car ran out of juice. Also, my gauge is wrong/inaccurate. Many times it goes all the way to the left on R and still when taken to a station for refueling, it takes in about 12 gallons. Very wrong gauge!!

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1999 Mercedes-Benz S600, 103K miles - garage queen
1988 Mercedes-Benz 560SEL, 89K miles - daily driver
2007 Hyundai Sonata Limited, 31K - daily driver

The contact disk at the bottom of your sender is most likely dirty/not conducting well and thus you were out of fuel before the disk finally made contact.

Its easy to get in there and clean the unit out...