Nirvana is a 64 foot Alden Cutter that displaces around 75,000 lbs in cruising trim. She is fitter with a 100 hp Yanmar that burns around 2 gph at cruiing speed and around 1 gph while charging batteries and running the watermaker.
When I get to the boat after Christmas I'll check the logs, but as I recall the largest fuel purchase we made was about 120 gallons, and the smallest was about 30 gal. Given the scarcity of fuel docks where you can be confidant of getting clean fuel it makes sense to keep the tanks fairly full.
Mexico is great, but we weren't able to sail very much, Nirvana needs about 6-7 kts to sail effeicently and a lot of the time that there was wind it was comming from the wrong direction. During 3 months in the Sea of Cortez we only sailed for maybe 10 hours, and we made 3 trips from La Paz to Loreto and back in addition to a lot of short hops from anchorage to anchorage.
Nirvana has a pretty effecient charging system, but it is engine based, and we would typically spend 4-5 weeks between Marina stops, so we burned quite a bit of fuel charging the batteries (900 amp/hour AGM).