I have a "gas"credit card. It is all I use it for. I received my roll up cost for 2014. My total gas, which is both propane and gasoline, for last year was $5,961.87.
As a guesstimate, I believe my propane was under $300. My mileage, well I need to look that up and it is not handy right now.
General area of driving was:
Start in Texas, New Mexico, Arizona, New Mexico again, Arizona again, Utah, Nevada, Oregon, Idaho, Wyoming, Idaho again, Montana, Wyoming again, South Dakota, Nebraska, Kansas, Oklahoma, Texas again.