If the Japanese and US test
If the Japanese and US test cycles are different than that would explain it. At face value the 37 km/l converts to like 84 mpg. 50 MPG on the combined US test cycle is what that car would deliver if it went thru the US tests. The 8% number comes from the 37 km/l and 40 km/l ratings which would come from the Japanese test cycle. see clear as mud. :)