Here is a couple of sample pages from my Excel spreadsheet:
I keep a separate sheet for my oil changes. The columns there are date, mileage, filter costs, oil costs, labor costs, total price, miles since change, oil description, filter number, plus some others, like engine run hours, gallons burned per change.
In general maintenance, I have columns for date, mileage, price, Itemized Service (I include part #s and description), and vendor. I also track on that page how many miles on key parts like brake pads, rotors, and tires.
One day, I
gotta see someone about this OCD thing....