If you stick the numbers in a spreadsheet you can quickly "see" what the savings are per mile, for your daily commute, per X miles, per year, and so on. I didn't buy the 35d purely for the fuel economy, but there are some nice perks compared to the 35i:

• Savings of $200 to $230 per year due to better average economy
• Average of 33 fill-ups instead of 39 fill-ups due to better range
• Difference of only $2.25 to $3.60 more per fill-up for diesel

All figures based on the average economy from fueleconomy.gov and the low and high prices for Colorado from gasbuddy.com. I've been getting 22-23 on average, which jibes with the 22 MPG combined posted on fueleconomy.gov, and I'm assuming the 35i would get the 19 MPG combined in similar driving conditions. I used 10k to 13k miles per year based on my daily 40 mile round-trip commute plus other trips.

What's funny is that the range of the X5 35d seems limited to me. My 2003 GMC Sierra HD diesel "only" gets 16 to 20 MPG, but it has a 34 gallon tank, so the range is typically 550 to 600 or so miles. I've never driven it on a trip without towing, but it might surpass 700 miles unladen. Not that I'd rather be in it over the X5, but not having to fill up often makes long trips nice!

On just the comparison note; my Peugoet 504 diesel carried 40 gallons of fuel.
15 in the main tank, and another 25 in an additional tank right behind the rear seat.
And yes I still had plenty of room in the trunk.

One year the wife and kids, luggage and all took a trip and clocked a little over
1300 miles before I had to fill up again.

yeah, my truck's got a big tank (40gal) and it'll go > 650 mi if i stay below 90mph....quite nice...on the other hand, the predicessor to the X5d was an 06 Sequoia that could only go 280 miles on a tank..that was rediculous...in the end, 500+ miles in the comfort of the X5 makes me want to take a long trip!

if i stay below 90mph.... i have the same problem. :D

i get 9 mpg in the Ford when towing my box trailer. my last trip was to PBIR in FL and i got 300 miles to the tankful. i'd have been there in under ten hours if it weren't for the forest fires and the damn GPS causing me to get on the turnpike headed in the wrong direction.

BTW i've driven a 335d. damn that is a fun car. :thumbup:

Diesel Fuel
 

If my calculations are correct, and that's always a stretch, I'm getting 33% better mileage with my X5d vs. my 2001 X5 4.4, which at today's current gas/diesel prices means my diesel fuel is effectively 32% cheaper than the premium that the 4.4 uses even though in hard costs the diesel is $.10/gal more at the pump. I'll take that any day!:thumbup:

My daughter just got a BMW 3 series 2011 Coupe 330d, believe its the same diesel thats in the current 7 series, anyway it flyers. If you just imagine putting the diesel motor out af a X5 into a sedan will give you an idea how quick it is.

I drove the 7 series with this motor and turned the knob on the dash to sports and it lit the tyres up! and a 3 series no where as heavy as a 7 series! this thing is a torque monster.

Hey, Diesel prices will drop once they go off the "winter blend" and back to the "summer blend" We've had a diesel in the family for over 20 years, and in CA it always goes higher in the winter months and then drops -- sometimes dramatically when they shift blends. Of course, it's supposed to hit 80 F here tomorrow...not sure why we need the winter blend! LOL

Prices also go up in the winter due to diesel and fuel oil being similar. Those damn northeasterners with their antiquated boilers.......