I have a 2010 Navara STX D40 space cab 2500TD auto done 48,000 . The best fuel economy I can get is 20-27L/100 doing 85-90 kmh with motor screaming @ 2500 -4000 rev towing a Jayco sterling 21.65.4 approx 2.3 Ton and without 14-17L/100 around the city. Other than putting a match to it, is...