95 e300d mileage issues after trip - PeachParts Mercedes-Benz Forum

connerm · #1 08-08-2007, 03:40 PM

95 e300d 191,000. Summary of my recent trip from Northern VA, to Harriman, TN (west of Knoxville):

Filled my 24 gallon tank in Woodbridge, VA, added the appropriate amount of Stanadyne fuel conditioner, and zeroed my trip odometer. Pretty much drove the speed limit (mixture of 60, 65, 70, and the occassional work zone) with the a/c on the entire time. When I arrived, mileage was 523. Did no driving once I was in Harriman. About 1/4 tank showing on the gauge. When I left Harriman yesterday, I filled up with about 17.5 gallons. By my calculations, that's about 29.8 mpg.

When I arrived home late last night, there was just less than 1/2 tank showing on the fuel gauge. Trip odometer showed 530 miles which seems correct because we made a short detour (Smokey Mountain Knife Works). When I filled up this morning, tank took about 13.4 gallons. By my calculations, that's about 39.5 mpg.

I would have thought my odometer wasn't working properly but the fuel gauge made me really take notice, and I know how far away Harriman is.

Notes:
Car was loaded down pretty good with family and luggage.
Tire pressure checked cold and set to MB specs found on the door frame.
Oil changed at 5k with Mobil 1 synthetic 15 50 or 40 (i think).
Very easy on the accelleration (not much choice with this model)
Fuel topped off both times. (I rock the car to get a bit more juice in the tank)
Second fillup was at a truck stop with one of those huge diameter nozzles.

Anyone care to comment on this? 39 mpg seems highly improbable.
I know mileage figures are best calculated over long periods, but this seems unusual, even for a trip. Could geography make a difference?

TMAllison · #2 08-08-2007, 04:01 PM

My guess is the 2nd numbers are in error and your next fillup will show very low mileage.

The truck stop pump probably dispenses frothy fuel, pumping as fast as it does, and the tank was probably not truly filled when the pump clicked off.

Whats your historical mileage?

tjohn · #3 08-08-2007, 04:11 PM

Sounds like normal variation to me. If you finished the tank out, even on the highway, I bet the mileage would have come down a bit. Perhaps you benefitted from a combination of good fuel from the trunk station, favorable driving habits and advantageous conditions. Others have occasionally reported high 30s with the OM 606. By way of comparison, my OM 617 126 on a couple of occasions has gotten over 30 mpg over the course of a full tank. Lowest has been 17 mpg, lifetime average during my ownership is 24 mpg.

connerm · #4 08-08-2007, 06:14 PM

Normally I get around 27-28. Because the fuel nozzle was so big and didn't fit all the way down the filler neck, I filled very slowly until I saw the foam come up the neck. I never leave the nozzle to shut off automatically. Too many times I've seen it stick open and pump fuel all over the ground or the side of someone else's diesel.

TMAllison · #5 08-08-2007, 09:56 PM

I suspect if it was foamy fuel as you say and that it appeared full but was not which was the cause of your super MPG tank.

WINGAS · #6 08-09-2007, 06:41 AM

I was going to say that 29 seemed light for that model, and 39 seemed high.

Chris W. · #7 08-09-2007, 12:40 PM

My '95 is very prone to a bubble in the tank preventing true fill-ups. At one station with a slow pump, the bubble seems to form, and at my other normal fill-up station with a truck pump which flows very fast, there seems to be less tendency to form a bubble. Opposite of what you might think. I track every single tank, and radical differences in mileage from tank to tank over the same route with the same weather are basically the result of the bubble factor, in my opinion.

Some diesel is also much more prone to foaming, IMHO, which will cause an incomplete fill up.

Since I've owned the car, (January '04) I've tracked 118 tank fulls over about 80,000 miles. 33-34 MPG, and my previous '95 did 1-2 MPG better for some unknown reason.

Rgds,
Chris W.
'95 E300D, 240K

connerm · #8 08-18-2007, 04:20 PM

Just filled up for the second time since my trip to Tennessee. After I returned, I filled up and calculated I got 39 mpg. My last tank lasted me 560 miles and I just put in around 20 gallons. Looks like I'm back to 27 mpg. Probably was a bubble in the tank or something.

lorenztl · #9 08-19-2007, 08:01 AM

My '95 E300D @197,000mi returns 27-30mpg around town, sometimes as low as 25-26mpg. At highway speeds usually 35mpg, however varies from 33-36mpg. I usually drive 5mph over limit and may hastily bring 'er up to speed.