15,000 miles a year.
20mpg for the 3.0 avg; 750 gallons x 2.00 = $1500
24mpg for the 3.0D - avg; 625 gallons x 2.20 = $1375
But...the Diesel also gets to 60 in 7.2 seconds, versus the gassers 8 seconds...
and has more torque, and I suspect though i've not driven one, better performance around town...
Now...let's assume you drive like me:
30k miles a year, with a lead foot. I average 14mpg out of the 4.4i I have, in town, and 19 on the highway. So, overall a 17.5 mpg. Past experience has proven that even with a smaller engine, I"ll get very similar fuel economy, because i'm giving it the boot all the time...whereas, the V8 has enough power that I'm not *always* dogging it, just most of the time.
I'd expect real world mileage of the diesel for me to be about 22mpg or so. Highway would be more, in town a little less, but 22mpg is probably a good figure.
17.5mpg (V8) at 30,000 miles/year = 1714 gallons x 2.00 = 3428 At $5/gallon its 8570 for the gasser
22mpg (diesel) at 30,000 miles/year = 1364 gallons x 2.20 = 3000. at $5.20/gallon is 7093 for the diesel
But...the new diesels qualify for a tax rebate of $1800.
So...yes...the diesel will probably save you money, especially over the long haul and if you do a lot of driving. For me, the extra mid-range torque would negate the need for a thirstier V8, with little loss of overall performance. The tax credit is nice. And when fuel goes back up, the difference will increase dramatically.
Why don't I have one? Can you see putting 30k on a new car in the first year? The depreciation would kill me. I'm looking forward to a couple years from now, when the diesels are available as CPO vehicle, and I'm ready to upgrade from my '04 4.4i.