Poor Fuel Economy .. 99 E300

[chris74]

Well, I guess the title says it all.

99E300, 156K on her .. and the fuel economy is almost always 25 mpg, all highway. My assuption was she'd get at least low 30's highway.
Yes, the car is new to me (though I had an 83 300SD and am my second TDI).
Starts well - regardless of temperature, the power is always on tap. The MAF was replaced - had a CEL for it, a few other odds and ends (air filter, etc. Basic maintenance stuff) A lot of smoke during strong accelleration. My first thought is she's dumping excess fuel into the cylinders, but how?
Where shall I look first?

[POS]

First look at a new fuel filter - that'll have a lot to do with bad mpg. Tire pressure while you're at it.

Smoke during acceleration (black smoke) is okay - A LOT of smoke could mean air filter (did you replace it?), another issue that I'm not aware of, or it's just the way your particular car is.

[Scott98]

I had the exact same problem on my 98 E300 as you and here is how I improved my economy from 28mpg to 34mpg:

http://www.peachparts.com/shopforum/showthread.php?t=145076&highlight=fuel

Good luck.

Scott

[nhdoc]

Now that I have had my '98 for two full years I can say that fuel economy always suffers in the cold weather. Check the air and fuel filters but don't be surprised if in spring you start to see economy closer to 30 around town and 34 on the highway. I routinely see fluctuations on the order of 10-15% on MPG and it is always lower in the cold...probably a combination of winter blend fuel and lower effeciency of the engines in the cold weather.