I've always done everything I do to my cars, but I cant be arsed with a spreadsheet. Sounds like a good idea thou.
at the moment I use a ickle notebook i keep in the glove compartment, use LH pages for any work/parts etc, RH tabled for record of every petrol fill up; date, mileage, cost, and quantity. its a bit anal I know, but have got into the habit, so just fill it in every time i fill up.
Maybe its pointless, who knows. my last car was stolen, with the book, which gave the teiving scrotes a full record of all the mods I had done to the car......DOH!