If nitrates can be reduced, then remediation in the exhaust emission could be scaled back. This would also boost efficiency.
This number is interesting. 1 Kilometer per liter is equivalent to 2.35214 MPG. 1 liter is 0.264 gallons and 1 km is roughly 0.6214 miles. So, to go from KM/L to MPG, the calculation is 40km x 0.6214 = 24.856 miles and one liter x 0.264 = 0.264 gallons. So you're going 24.856 miles on 0.264 gallons or 94.15 MPG.
Show me any car currently getting 94 MPG. And to increase that performance by 20%, would basically make a car capable of 113 MPG. Ain't happening. Better MPG, yes, but nothing in the 90 to 113 MPG range.