Thank you for all reply`s
It is a 96 XCab 2.4 Turbo Diesel with sas 5.29 and 38" tires.
Around 4700 lbs
Before dual it used 0.29 gallons on 6.2 miles or 1.1 liters on 10 km
now it use 0.4 gallons on 6.2 miles or 1.5 on 10 km

I understand that there would be more drag and weight when an extra tcase are mounted.
but I think that all the stuff are the answer for my MPG,more weight less MPG

Thank you anyway