I got this idea from one of the V10 guys who posted this stuff. I thought it was cool, so here is mine.

--==WARNING: RAW DATA==--

Oil

Motorcraft Dyno Oil - 13.3 MPG 40 Fill Ups
Shell Rotella T6 - 13.4 MPG 74 Fill Ups
Shell Rotella T6 - 14.2 MPG 61 Fill Ups
Shell Rotella T6 - 13.9 MPG 15 Fill Ups (to date)



Air Filters

Stock Drop In - 13.9 MPG 18 Fill Ups
6637 Replacement - 13.5 MPG 125 Fill Ups (Aprox 22,000 miles)
6637 Replacement - 14.1 MPG 45 Fill Ups (To date; Aprox 7,000 miles)



Air Filter Replacement (6637 to 6637)

30 Days Before 6637 Relacement: 14.2 MPG 12 Fill Ups
30 Days Following 6637 Replacement: 14.4 MPG 16 Fill Ups



Fuel Filter

Changed: Aug 5, 2011
30 Days Before Fuel Filter Relacement: 13.3 MPG 12 Fill Ups
30 Days Following Fuel Filter Replacement: 13.3 MPG 11 Fill Ups

Changed: April 4, 2012
30 Days Before Fuel Filter Replacement: 14.4 MPG 12 Fill Ups
30 Days Following Fuel Filter Replacement: 14.0 MPG 12 Fill Ups



Other Data
Mileage from first 30 days after purchase: 13.6 MPG 23 Fill Ups
Mileage from last 30 days: 13.9 MPG 17 Fill Ups

Price of Diesel when truck purchased: $4.449/gal (28 Apr, 2011)
Price of Diesel at last fill up: $3.799/gal (7 June, 2011)

Average MPG: 13.68 MPG
Highest MPG: 18.22 MPG
Lowest MPG: 9.59 MPG
Total Fuel Costs: $9,093.69
Total Miles: 29958.1 Miles
Total Gallons: 2190.38
Cost per mile: $.30
Average Cost per Gallon: $4.159/gal
Miles Per Per Day: 73.61 Miles

 

Interesting info.
Here are some numbers from my log.

Average MPG: 15.322771
Average price per gallon of fuel: $2.895
Cost per gallon in 2003: $1.239
Cost per gallon in 2012: $3.988
Total Gallons used: 18,921.838
Total cost of fuel used: $54,783.56
Total maintenance costs (fluid, filters, tires etc): $6711.00
Total repair costs: $8900 (includes $4003.00 for trans rebuild)

Operating cost per mile: $0.2438
Total cost per mile (includes vehicle purchase price): $0.3221

 

New raw data:

Grey Ford CPS: 13.5MPG (106 Fill ups, 21988.9 Miles)
Black Borg Warner CPS: 14.4MPG (47 Fill ups, 9208.0 Miles)