Snowman9000 wrote:
When paying $1.69, it doesn't matter as much, but I have gotten a handle on our 25' Chevy 4500 Class C's mpg habits. 
60-65MPH, neutral conditions: 10 MPG
tail wind:  11 MPG
head or strong cross wind: 8.5-9
Mostly with cruise control ON.  No toad.
I maintain a log book for every gasoline fill, battery change, oil change, shock change.  I have entered that into a MS Excel spreadsheet that calculates the tank fill MPG and the OVERALL MPG.  My smaller unit with the 5.7L has narrowed down to 12.1 MPG overall.
Snowman9000 - Based on your numbers your cost per mile is $0.169 ($1.69 divided by 10 MPG).  Those driving the Sprinter or other diesel might have a cost around $0.136 per mile ($2.85 divided by 21 MPG).