For me it was because my first diesels were back in the 80's, an 84 Isuzu P'up and then a 86 VW Jetta TD. Fuel was extremely foamy that, especially in the cold winter months in Utah. If you didn't wait for the foam to settle, and top up, wait and top up...you'd drive away, and look at the gauge and see you at 3/4's of a tank in few minutes. So, for me it's just a bad habit.

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1983 W123 300TD US spec Turbo engine, with Euro bumpers and manual climate control, and manual transmission.

I do it so I can go just that little bit longer between fill-ups. I also love saying that I get "right at 600 miles per tank".

I agree. Both my 69 220D and my 83 240D go over 500 miles before the light comes on and I drive 600 miles before I stop for fuel. Even then I have between 3.5 and 4 gallons in reserve. No need to top off and risk a bad case of diesel foot with that kind of range.

BTW: both my cars have been swapped from 65 liter (17 gal.) to 78 liter (21 gal.) tanks.

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1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

Your figures don't add up. There's NO way your cars get that much over 28 mpg between fill-ups. NFW at all. In fact, your cars do not get 28 mpg, ALL the time.

is there any way to tell or find out what the size of the fuel tank is in the car?

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All gave some, Some gave it all ~ 9-11-2001 Never Forget

People shouldn't fear their Government, The Government should fear its people.

I was reluctant to mention mileage because there is such a wide variation in what people report but my cars get between 33 mpg and 35 mpg every time. Which works out to between 561 and 595 miles for 17 gallons. Since I have 21 gallons I find that I can safely wait 600 miles between fill ups.

Odometers in both cars are GPS verified and have been torn down and checked to have the correct K value for the differential. You can't trust the stamp or tag since there is a lot of speedometer swapping. My 240D had a 280 speedometer when I got it. Tires are as close stock diameter as possible.

Even my tired 71 220D did the same. Worst tank in my 8 years of ownership was 30 mpg and that was due to hours of idling over the winter while the car was moved for snow plowing. Of course that one was burning a lot of oil too.

However there are a few qualifiers. I have OM616 engines and manual transmissions. I don't use AC and my W115 has manual steering. I live in a rural state with a 50 MPH speed limit. I have to drive 15 miles before I hit my first stop light. I can drive for miles without touching my brakes. I rarely end up in traffic nor do I spend much time on interstates. I fill up at the same station/same pump every time.

If I had a 300D automatic in an urban/suburban area I would expect much less.

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1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

The attached photo shows the difference between the 17 gallon and 21 gallon W123 tanks. The trouble is they look the same from the trunk side. It may be possible to see the inside profile by removing the first aid kit.

If your low fuel light is trust worthy you can fill up when it comes on. A 21 gallon tank will take about 16 - 17 gallons to fill and the 17 gallon tank will take about 12 - 13. Mercedes reserves are pretty conservative.

All of this goes out the window if you've ever had a plugged vent!

Attached Thumbnails

 

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1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

Given your situation that mileage sounds plausible.

I get around 25 pretty consistently. I drive like a jackass, but I have a manual transmission, don't brake any more than I absolutely have to for turns, do less than half city traffic, and have a hotter than stock thermostat.

I fill to the brim for consistency in mpg calculations, to get as far as I can between fuel ups, and because it's just a habit for me.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Nut-uh. 6 MB diesels, 2 Million miles covered, most bought new since a new 220D in 1969. NONE of them got 30 mpg ALL the time - ever. Real world mpg on these cars is; mid-upper 20s average at best. Your claim isn't reality.

Almost all vehicles on the road have a tank that does not fill 100% like one would think. There is always air at the top of the tank to allow for thermal expansion. The minimum percent is calculated based on the volume of the tank and the maximum expected temperature fluctuation for the expected fuel type. The fill tube actually extends a little bit into the tank so that when it is filled, a certain amount of air space remains at the top of the tank. Under normal conditions, your fuel system should never be venting raw fuel.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

25 mpg is closer to reality. His figures don't add up, according to his own set of claims.......

All right you've got me. Last year my Son, my Dad and I covered 4300 miles during an 18 state trip to visit family and friends and I only averaged 32 mpg with a 5 speed. Fun trip too!

Seriously though I've seen this argument time and time again and the reported mileage is all over the place. The differences are consistently huge and I believe everyone - except the 40+ mpg Craigslist ads!

I wish I knew what caused the difference in reported mileage. I've verified odometer accuracy to within a fraction of a percent over 100 miles with GPS and mile markers. I've disassembled and verified the odometer gears for correct K value. My numbers are correct. If my odometer slipped they'd be worse. Plus it's in the fuel consumption chart on page 30 of the 220D owners manual. The US gallon line intersects 50 mph at 35 mpg. Vermont state speed limit is 50 mph.

In my part of the world 34 mpg is average. Put me in an LA commute and things might change. Given how many folks claim mid twenties out of an otherwise properly running 220D/240D I believe it happens regularly. However, according to the chart you'd need to travel at 70 mph (all the time!) to land in the mid twenties. Are folks running wot for every acceleration? Hours of idling? AC and automatics? I can tell you power steering doesn't make much of a difference. Perhaps it all comes down to driving conditions but I've never seen mileage that low. Even a local 300D owner (NA auto) claims an average of 30 mpg.

During the trip I never dipped below 31 mpg and I did full tanks at 70 mph. They were the ones that dropped my trip average. I stayed out of the twenties even then! However I do have a 5 speed which gives an effective 3.18 differential ratio. My 4 speed 240D might not have fared as well at 70 mph.

I've been approached by a few former 220D owners and invariably the conversation turns to the 500 mile (stock 17 gallon) tanks followed by the great handling and brakes plus you don't even need the broken heater fan and the water in the trunk and the rust and....

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1969 220D 5 Speed (OM616)
1983 240D 4 Speed
1985 300D Auto 376K
1985 300D Auto 275K

Oooh this is a good thread.

My car's manual says it has a 65 litre tank. That's okay.

When filling up, the bowser clicks off at around 65-70L. That's okay, I don't always have the same conditions (temp, car on lean, different bowsers, whatever) when filling up.

What confuses me is that sometimes, I can get 75+ litres in easy peasy. Last time I filled up I put in 75.92L using the top-off method. I've put in 80L previously if I really drive it til it's low.

So with the mention of the 78L tank above, is it possible my car has one, and the manual was wrong? I know it's steel if that makes any difference

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

OK, so I'm still normal ?
IIRC, weren't many/all of your family's cars automatics? That alone would make your mileage figures totally irrelevant irrelevant for direct comparison purposes. Furthermore, notice that he "5-speed". Even if you had a 4-speed manual or two, what you report is still totally irrelevant for the purposes of a direct comparison.

Have you ever even been in VT? It's 50 MPH most places, no traffic, no stop signs. Pretty much ideal for a 4-speed manual and awesome for a 5-speed manual.

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

VT220D, where in VT are you located? If I ever get the 300SD up to VT, it might be fun to stop by -- I've never seen a 220D or an OM61X/5-speed in my life before .

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."