To go to the new '07 4.6 I would need to budget more for gas. Currently my '04 Sport Trac 4x4 w/3.73's gets 17 mixed and 19.5 freeway. I'm a little miffed my coworker gets the same fuel mileage with his shortbox crewcab 4x4 GMC with V8 power. Since I use my vehicle 80% of the time for work and...