log book
I use a hard cover ledger type book from office dept. It has 200 pages and several vertical colums on each page. I divided the book with roughly 1/3 devoted to maintence and 2/3 to fuel mileage. It rides in my center console with a small calculator so I can do my mileage before i leave the pump. It works good for me.
Some things I write in it are: date, type of maintenace, who preformed it, was it under warranty or TSB work if at the Dealer, mileage at time of work, mileage for next service ( oil, fuel filter etc), misc info colum.
Fuel gets : date, overall mileage, trip mileage (reset each fillup) calculated mileage, fuel pressure at idle while siting at the pumps, location fuel purchased from, if its not my regular station. MIsc info colum, which usually gets price and driving characteristics for that tank.
my 2 cents
J-