I average 18.5 liftetime according to the OBC with my '03 3.0 with 5-speed manual, and 20" staggered wheels/tires, which I know cost me about 1-2 mpg because of the weight. I run 33 psi front and rear, Toyo Proxes ST II tires.

When i calculated the last fillup manually (miles driven on the obc divided by amount of gallons filled up, I reset each fillup), I was at 18 mpg even. I drive mixed, about 60% highway and 40% city driving on a tank.

In my opinion not bad for a 3 ton SAV that is 10 years old, of course if i went back to factory 17s or 18s the mileage would probably improve but I love the looks of my 20s way too much.

Low rolling resistance tires make a huge difference- as does "over inflating" them... 50 psi was what I used to run on my Hondas. A slightly rougher ride but never had a issue... I agree with the above posts regarding hills- use the down hill to maintain or gas it a little so the next up hill requires less input.

Buy a Toyota Prius :)

^Nissan Leaf is better ;)

If you're going down hill coasting in top gear and keeping your speed, the FI is not injecting fuel. If you put it in neutral the FI needs to provide fuel to make the engine idle, then you'll need to brake to maintain your speed. Yes, lifting in gear slows the car down. Is putting it in neutral and back in gear at speed going to cause excessive wear on the AT? :dunno:

For my money, just avoid tromping the gas and unnecessary braking to get decent economy. Make sure your tires are properly inflated and get excess crap out of your car to keep the weight to a minimum.

One day I was stuck behind some turd in a Civic doing 80kph in a 110 zone and had a "Don't Honk I'm Hypermiling" sign on his trunk. I kinda wanted to punt him into the ditch...

Not sure if its a thing that is done/used in the US but here in the UK It is something that is commonly carried out to large engined motors and thats to LPG the vehicle, thats where the petrol fuel system is supplemented with a Liquid Petroleum Gas set up with 8 injectors mounted and a piggy back ECU that runs them and cuts the petrol out and runs solely on LPG and if the system is fitted by a reputable company you lose no performance and the only thing that comes out the exhaust is water vapor so its a super clean burn my oil changes (every 6k) the oil comes out as clean as when I put it it and thats no exaggeration.

I get around 18-19mpg with spirited driving but with the cost of LPG half the cost of petrol you are achieving a cost comparison mpg of 35-37mpg that makes running a big V8 cheaper than a 4cyl BMW sedan.

Yeah, a lot of taxi cabs here are LPG, as well as some pickup trucks. It's tempting.

No arm wrestle people but I have to be honest with you. I knew when I bought the X that it was an 8 Cylinder vehicle that begged to be driven. After all it is a BMW. So really why should I nitpick trying to squeeze the most MPG out every drop of fuel. I'm thinking just drive like someone with a brain and every now and then have some fun. The conclusion is.... LG.

Oh, if I had the 4.6 or 4.8 I wouldn't even try to hypermile. With the 3.0 I'm having fun with it as sometimes I get long stretches of 10L/100mkh on the gauge, and since I work from home (mostly) I'm never in a hurry to get anywhere. Of course, my right foot still gets heavy on the freeway now and then ;)

Like you say Professor "An intention without a decision is just a wish." I intended to buy a BMW, but I didn't wish to save fuel when I bought it. That to me would have been wishful thinking......;)