I haven't posted the final numbers yet, just filled up last night.

I will say that filling this tank to the top is a real PITA. Each time was about 15 minutes messing with the foam and waiting for it to gurgle down. It also does weird things to the fuel level indicator. When I first started out after filling up, the gauge read full then quickly started dropping. It looked like I was hemorrhaging fuel from somewhere because the gauge was literally moving before my eyes. It dropped down to about 3/4 then slowly rose back up and then fell again.

I ended up stopping to make sure there was no leaks from anywhere. All was good so I went on with the drive. My observation was that you can cram about another 2 gallons in there after the first click stop but it takes forever. Also, the MPG figures were in line with my previous readings where I simply let it click off and then continued until it clicked off again after a short pause.

When I get home this evening, I'll do a screen shot of my spread sheet with my stops and average speed calculations along with the gallons used and mileage, etc...

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Glad I'm not the only one who finds it a pain to fill the tank. There doesn't seem to be a lot of rhyme or reason as to when the gauge reads full and when it reads somewhat less. I won't worry about once I'm done with my MPG calculations. But, until I come to some firm conclusions, it would be nice to remove the pump shutoff variable from the equation.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Is there a vent in the filler neck (actuated when the cap is screwed on)? If so, press on it to release the trapped air for faster filling to the brim of the neck. VW diesels have it, I'd imagine Mercedes has something similar.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

No vent that I know of. You pump, it foams up and stops. It goes down quickly at first but then goes slower and slower - foam, stop, wait, foam, stop, wait like, 50 times just to get the last couple gallons in.

All that fuel above the 'full' indication makes it look great like going almost 500 miles on a half a tank and I'm sure the range is extended but for every day driving and MPG calculations, I don't think it's worth it.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Am I correct that, unlike a gasser, there's really no risk in filling a diesel very close to the top?

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

So, here's the (not so) exciting results:



The "In Out" times are places I stopped the car and turned off the engine for a period of time so this didn't contribute to the average speed calculation.

The section above the yellow line is the trip up and the area below is the trip back. The trip up consisted of about 2 hours of interstate, an hour of sitting stopped in traffic at various times and the rest was a combination of rural highway and small town speeds of 35 MPH or less. I did get trapped behind a few pokies on the two lane back roads so I lost a little economy when I had to leave them behind in a cloud of smoke. Not really trying to smoke them, it's just a byproduct of acceleration. The trip back was all interstate except for the first 30 minutes getting through town. I have EZ pass so there was no waiting at toll booths.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Evan, your 33.3 combined certainly seems to be within the margin of error for the rated mpg....and of course you do a wee bit better because of some of the mods you've done.

Thanks for the effort and documentation.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Nice work, thanks for sharing. Entering data into fuelly at every fill up seems a lot more straightforward and less prone to error. As long as you account for every gallon into the tank and every mile traveled, any pump variation will average out. I just keep a running total of the trip odometer.

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CENSORED due to not family friendly words

I have a record of every gallon of diesel used and the mpg for every fill up for the past fourteen years and 150,000 miles. I have it for thirty-two years on my 240D. IMO the only way to get really accurate as to what your mpg is, is to do it over several tanks of fuel and several thousand miles. I don't plan to add up all the data for mine, but suffice it to say that the average for my 210 is in the upper 20's and for my 240D it's in the mid-20's. My 210 has shown a few as high as 34 mpg, but the next tank would usually bring the average down to more normal numbers either because of foaming fuel, filling up on an incline or whatever else may have affected it.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

On my 124 I have found that even a slight angle on the car (driver side down) when filling up is worth close to a gallon extra fill. I know this because my main filling station is like this, there is a concrete pad which transitions to asphalt causing a slight down angle. But since I use this place all the time I know my MPG results are quite consistent.

Rgds,
Chris W.
1995 E300D, 426K

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Objects in closer are mirror than they appear.

Fuelly looks pretty slick....I just signed up. If you browse the cars, you'll see a total of 10 98/99 E300's. Over a combined total of 145,000 miles, average mpg is just shy of 27. About what one would expect.

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 179k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 77k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

That's correct. His number is well within the ranges given for that car - even unmodified. Since he was driving trying very hard to maximize his mpg in the distance covered, I would have almost expected a lot better number than what he reported. Esp. since he stated all the low-speeds he was driving the car at. You can get in one of those cars without even trying to subconsciously 'hypermile' as was his intent, even if subconsciously, and get 30 to 32 mpg at very high speeds.

'27' is a very kind number IMO for that car collectively. In 131K miles, that number is way optimistic, from the mixed use my 99 E300 returned. Keep in mind that ALL the fuelly posters are actively trying to maximize their mpgs 100% of the time. Even if they're in a hustle and bustle, they're still trying to maintain their superior reporting numbers. So, that's a skewing of the effort right there. Which is not reflective of the non-'hypermiling' car owner mpg numbers.

After 14-years driving a 99 from new, you don't have to track your mileage, IMO. It's somewhat a waste of time, when you know what the car routinely returns.

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'06 E320 CDI
'17 Corvette Stingray Vert

Wondering why anyone would think that the fuel gauge was any indication whatsoever to the mpg your car was getting? That's a new one to me....


Unless any reported mpg calculation can be quantified with 100% of the control points and scientific data points to reflect exactly how that conclusion was arrived at, and why it was accurate - well, it's an exercise in non-scientific seat-of-the-pants raw data, and suppositions.

The closest mpg calculations I've read have to do with defined and controlled test conditions - not one mpg test like that has ever been done on this forum to my knowledge.

The only way to control most all those variables as well as define them aren't going to be on any public domain, driving in a variable, non-scientific cross country manner.

__________________
'06 E320 CDI
'17 Corvette Stingray Vert

Evan-just think how miserable the results would have been had the license plate bulb been working.

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1999 E300 Turbodiesel 169,000 miles
1986 Porsche 944Turbo 20124 miles
1948 Dodge Deluxe 4 door 66521 miles

Nope, it's actually a very useful metric to keep track of, as it can help alert you to problems with the car.

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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."