From February to November, i'd say about 50-100L ( 13-26 U.S Gal. ) / Month, between my 2 cars, mainly from my daily driver Peugeot which gets 47 MPG.
From November to February i'm basically unemployed so it's entirely possible that some weeks i might not start either of my cars at all, and i'll just use my bicycle, however in these months i mostly drive around in the Capri, so no more than 40-50L ( 10-13 U.S Gal. ) / month in these months.