OK, so I'm driving the 300Tdi now!
Once I got the odometer set up correctly and all, I went and filled up the tank. Before that I estimated my miles done for 1/8 of a tank and was looking at 20 MPG.
The needle was just below the middle mark when I filled up, and it took 10.01 gallons. Now the needle is just above the middle mark, and I've done 191 miles, this means that if I estimate 9 gallons to full, I'm only getting 21.2 MPG.
I'll make it official and get a fill up when the needle gets to 1/2, maybe tomorrow -- I want to know how many gallons it will take when it shows 1/2. But getting 21.2 MPG seems a bit low, even though I've done some experimental driving and some idling.