I just want to show you guys my fuel log from today, but I can't post the link because I have too few posts, so just click the car under my name.
I bought my TDI one month ago as an upgrade from a '91 Chevy pick up truck that was averaging about 17mpg highway. I make the round trip from Salt Lake to Las Vegas several times per year, and it was typically costing me over $200 in gas per trip. Now, I can say I'm more than proud of my investment: with a little bit of diesel additive, duct tape on my grill, and utilization of constant throttle/EOC driving, I've managed a 51 mpg tank with my otherwise stock 2006 Jetta TDI - 38% above the EPA highway rating!
That at a fairly reasonable average speed of 65mph not including the stops I made.
A couple of weeks ago, I was starting to doubt my goal of 900 mile tanks, but at this point I'm considering shooting for 1000! I can't wait to see what this car can do, especially after I smooth out the belly (which no longer has the OEM belly pan). This site has some great information, and I'll be sure to keep you guys updated!