 As a result, the maximum power generated by the V-1650-3 in "high blower" was at , using 61" Hg.The V-1650-7 used in later P-51B/Cs and in the P-51D/K produced slightly more power but, because of the use of slightly different gear ratios for the impellers, the critical altitude ratings of the supercharger stages were lower, and , respectively, since experience showed most air-to-air combat over Europe was taking place between these altitudes.The power of the engine could also change according to the octane rating of the aviation fuel being used.