Yesterday I filled the tank and recorded 25 mpg
Got home and checked the oil and was 1.5 qts low; she burns about a qt every 1000miles. Topped it up with Rotella 5-40 and today took a 100 mile drive.
Filled the tank back home and recorded 22 mpg
Driving circumstances were:
300 miles of mixed town and rural with speeds generally 50 and under, some stop and go, plenty of idling on cold mornings for the 25 mpg run
100 miles of mostly 50 and over with full throttle runs over the mountain passes and fun on VT RT 100 one of the finest drivers drives there is.
No idling = 22mpg.
Any feedback?

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

Makes no sense, its moving the same amount of oil either way.....I'd attribute it to different fuel qualities, wind when driving, more or less hills.....accelerations.....etc.

Also, 100 miles is way too short to make a good reading, you only burn like 3.5-4 gallons driving that far, completely inaccurate.

MPG needs to be averaged out over several whole tank uses in similar driving conditions....like on a real long freeway trip.

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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)

Windage? (when the crank churns the oil in the pan). Some engines have windage trays to prevent this.

I doubt it, the pan holds probably 4.5-5 quarts, the oil filter assembly has another qt....oil cooler and lines another.....and say about 1+ is going through all the passages at any given time or is up in the head/valve cover...I doubt the oil level is "deep enough" along the upper oil pan to have oil churn.....this is a MB remember.

Plus I doubt it would sap 3mpg worth of economy/power.

__________________
-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)

Some of the windage trays claim about 5-10 hp gain. I usually calculate about 2 more mpg for each 5 hp that is freed up.
Tom

I would say it is a coincidence. Mileage is best calculated averaged out over many fill ups to eliminate high and low occurances.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

If the crank hits the oil, you'll know it. Lots of smoke and possible runaway engine.

Even with the oil to the full mark and the engine off (all oil in the pan) the oil doesn't touch the crank.

__________________

Gone to the dark side

- Jeff

I would say it is nothing to do with the car or oil level and all about driving down in elevation for 100miles then going back up.

I disagree, if there was a true delta, it would be from viscosity.

Although, I'll tell you, when I freshened the cyl head on the 606, itg started burnring oil. 1 qt every tank ful ( 700 miles), and it does sdo MORE when the dipstick is topped off, rahter than low, regardless of age ( viscosity) of oil.

Anomolous to be sure. I was also thinking windage.

The only way i could see oil impacting fuel economy is if you are using a heavier oil than whats called for but not low oil.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Guys who own "ricers" leave their oil low on purpose, they think there is more power that way due to less 'oil slinging' on the crank.
Some people will do anything to try and beat mustangs and such and at a drag race. My friends down the street have (did, economy) dozens of honda/toyota blocks and heads to be 'modded' (another ricer word) in this vain and expensive effort.

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'01 Escape 2.0 5 speed- 101k
'96 Cherokee 5 speed- 120k
'92 Mercedes 2.5l turbo diesel- 212k
'90 Aerostar ext Cargo 4.0- 29k
'02 ZX2- 93k
'98 F250 CNG- 54k

Just put 0w20 in it and run it 4 qts low i bet u could go another 50 miles.. lol but seriously like others have said the large size and shape it's unlikely to have much impact at all less than .5 mpg.

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

Consider the difference in temperature on those successive days. Cold weather lowers mpg dramatically.

Indeed. My car dips below 30 mpg on those single digit days.

The weather was similar on both days.

__________________
1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily