A Honda Civic with a D17A1 engine, at idle, with all accessories off, at 700-720RPM, reports 0.6-0.7L/h, or 0.17-0.19 Gal/h over OBD-II. Vent Fan to Full and Mixer to Hot without A/C reports 0.9-1.0L/h, or 0.24-0.26 Gal/h.