My cars always have a bound 3x5" logbook. Gas purchases are recorded on one side, and any repairs/maintenance (oil changes, brakes, tire rotation/winter changeover) is noted starting on the backside. I have yet to meet in the middle! Oh, and I typically keep my cars until dead... My current car is only four pages of gas purchases in 33k miles... My old truck with a thirsty 460-inch engine used only 30 pages on the gas-side in ~125k miles.