One mile is equal to 1.609 km One gallon is equal to 3.785 liter Which implies 37.5 miles/gallon into Km/Liter will be (37.5*1.609)/(1*3.785) kilometers per liter. so 37.5 miles/ gallon will be 15.941 km/L. The conversion factor was 1.609 divided by 3.785 . Which is 0.4250