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.