TRAVERSE CITY, MI – Auto makers facing stiffer U.S. corporate average fuel-economy standards likely will offer more small cars at the risk of consumer rejection, and the public doesn’t appreciate the struggle to squeeze greater efficiency out of today’s vehicles.

That’s the consensus of panels at today’s Advanced Powertrain Forum at the Center for Automotive Research’s Management Briefing Seminars here.

New CAFE regulations require that auto makers achieve a fleet 35.6 mpg (15.1 L/100 km) by 2016 and 54.5 mpg (23.2 L/100 km) by 2025.

But meeting those standards by building smaller models may strand the vehicles on dealers’ lots, says Justin Ward, advanced powertrain program manager for Toyota.

“What is the market going to be willing to accept in the timeframe?” Ward says. “One idea (by OEMs) is to drive toward a smaller, lighter-weight vehicle. But if a consumer still wants a vehicle larger, bigger than their last new vehicle, then we’re not providing the customer (with) what they want.”

General Motors’ Charlie Klein, director-global, mass, energy and aerodynamics, says consumers have no idea how difficult it is to achieve 8% fuel-economy improvement “and how hard we work to get deliver it.”

However, he argues, competitive pressures trump government regulations as auto makers strive for the technological innovations that boost fuel economy.

What’s not clear is what the new CAFE rules mean for pickup trucks and other larger vehicles.

Dan Kapp, director-powertrain research for Ford, the U.S. leader in sales of pickups with its F-Series model, says CAFE’s effect on pickup sales largely will be driven by consumer reaction to fuel prices.

This year, the high cost of gasoline has driven buyers to Ford’s 3.5L EcoBoost V-6 engine. A small V-6 in a fullsize pickup at one time might have been considered “blasphemous” by truck owners, he says. But they now are opting for EcoBoost at a 40% take rate.

However, higher CAFE standards may result in “fewer trucks in personal use,” he says. Regardless, Kapp promises, future Ford pickups will be lighter and more fuel efficient.

Raising mileage has been and will continue to be a “dog fight,” Klein says. “We bring out our best hardware, and a year or two later somebody else brings out their best hardware.”