I too have a ring binder for receipts, another for registration docs, Mots & history.
For maintenance & notes on each of my cars I use A5 hardback note books (I am on volume 6 on the Pembleton!) & an A5 index book for part numbers and cross references, eg. O for Oil filters, T for Timing Belts etc and a A4 sketch pad for drawings where parts have to be made or modified.
Works for me.
