Hello everyone,

I am a proud new owner of a 300d . . . my first Mercedes and planning on running on a WVO/diesel mix for my commute is 45 miles each way. Purchased it with no records from a kinda shady dude, but it was in good condition with 162K miles. Everything works except the Radio and the Heater. It's a pleasure to drive and it loves to go 75 mph. I had a couple of questions for y'all if you'd be so kind to lead me in the right direction. I did tons of searches and have read conflicting answers.

Heater: I had the monovalve and its housing replaced to no avail. I was told it was the temperature controller not grounding and needed to be replaced, but I didn't want to be had for another $300. All the buttons work, but the center vents do not blow air.

Operating Temperature: I replaced the thermostat with a new 80C unit, but my engine hovers at +/- 100C. I heard that this is normal from some people, and too hot from others. I plan on doing a whole coolant flush, but is there anything else I can do to keep the temp lower?

Blowby: I have some, but how can I gauge how bad it is? My filler hole blows steam when the cap is taken off, but the cap slowly jiggles as it's loosened and doesn't act like ol' faithful.

Gas Mileage: It gets around 21-23 MPG average. That's taking the miles driven divided by the amount of diesel to fill the tank. Is this normal? And is there any way to increase the #'s? 45 mile commute each way and could take a toll on my pocketbook. I heard diesel purge . . . but any other suggestions.

Rough Idle: Rough idle, but smooth sailing while cruising. Mechanic said that the IP dampener is the culprit, but don't know if it's related to the blowby and poor gas mileage. help . . .

I thank everyone for reading this and for offering your priceless knowlege.