Eh, you won't see wheels pushed outside the wheel wells as a normal thing - that hurts fuel economy directly, far more than the benefits in footprint.
For what it's worth, the Passat TDI with a manual gets 46.4 mpg on the CAFE (1978) combined cycle, and that is the most efficient diesel-powered vehicle currently available in the US. (38.2/62.8 are the base numbers, so on the 1985 cycle, that'd be 34/49, 41 combined, when compared to original sticker numbers on a PD or earlier.)
The following MY2013 vehicles beat the future 54.5 mpg CAFE requirement:
Toyota Camry Hybrid XLE: 54.8 MPG
Acura ILX Hybrid: 54.9 MPG
Lexus ES 300h: 55.2 MPG
Toyota Avalon Hybrid: 55.2 MPG
Toyota Camry Hybrid LE: 57.4 MPG
Honda Insight (CVT): 58.8 MPG
Toyota Prius v: 58.8 MPG
Honda Insight (selectable ratio CVT): 58.9 MPG
Volkswagen Jetta Hybrid: 60.8 MPG
Honda Civic Hybrid: 63.1 MPG
Ford Fusion Hybrid: 66.1 MPG
Lincoln MKZ Hybrid: 66.1 MPG (exactly the same results everywhere but the sticker MPG as the Fusion - something screwy is going on here, and the sticker MPG, even unrounded, is exactly 45 on the MKZ)
Ford C-Max Hybrid: 66.1 MPG (exactly the same results everywhere as the Fusion)
Lexus CT 200h: 70.6 MPG
Toyota Prius: 70.6 MPG (exactly the same results everywhere but the sticker MPG as the CT 200h - the CT 200h has much lower sticker MPG. Might be because of the higher speed tests, in this case, as the Prius has better aero)
Toyota Prius c: 70.8 MPG
Pickup trucks will need to change a lot to get better fuel economy, but it's certainly doable. Aero will be hard to do, but some can be done by switching to transverse FMF drivetrain layout. Further help here can be found by hybridizing, and using the hybrid system to power electric motors on the rear wheels to get AWD, which will also allow lowering the load floor (no more differential). The Power Split Device could be useful here, too, to keep the engine on full boil relatively efficiently.