 The Bf 109 G-4 was "up-gunned" as well to the Bf 109 G-6, with two MG 131 machine guns replacing the MG 17, and supplementing the MG 151/20 cannon in the nose.The MW 50 (water-methanol) additive increased lower altitude performance but the increase in weight reduced manoeuvrability.German pilots were critical of the Bf 109s fragility, but praised the Fw 190s strong construction; the latter type remained the preference among western theatre pilots.