Do you have a way to find how much was charged on the company gas card?

I saved and scanned all of my fuel receipts, so yes, I can get that number. The tricky part is that this is my work & personal truck (75% of my 2016 miles were for work). I filled up my truck once a month (or if I went on a non-work related trip) myself to try and offset the fuel cost of my personal miles.  The amount on the company fuel card was $2,205

What do you mean "try to offset the fuel cost of my personal miles"?  In any event, The company paid you $4500 plus gas and it's that sum that you would be comparing to the flat mileage rate.

I was referring that I don't expect my employer to pay the fuel cost of my personal miles. So if I would go on a trip that is not work related, and consumed a tank of gas during that trip, I would fill the truck back up out of my own pocket. That amount is not part of the $2,205.

I was just trying to make sure that nobody was planning on using 75% of the $2,205 as part of the calculation, but in turn made my question a bit more confusing. My apologies.