Nice screen shot. Though I do have a question as to why excel? Just export it to a CSV txt file. Excel and other programs can import them just as easily.
Price, Mileage (Odometer reading), and Gallon/Litre should be the only things in the top of the form. You can have a check box for litre or gallon, and then the drop downs for the type (Octane) & other info as need be.
I see this more as a fun tracking program though. I like it, but it might not be everyone cup of tea.