Uses 4.5 quarts (4.26 liters). I use Mobile 1 V-Twin 20w50 Synthetic with the Harley-Davidson Syn3 filter (filters down to 10 microns). I compared specifications of all oils and this is the best oil on every spec except high-temperature shear-strenght in which AmsOil 20w50 has Mobile 1 beat. But since it is a liquid cooled engine the additional shear-strenght will never be a benefit. Mobile 1 V-Twin oil retails locally so easier to get.