Although recreational vehicle manufacturers have been striving for greater fuel efficiency for half a decade, the movement began seriously gathering steam over the last two or three years as the nation's average gasoline price rocketed from just over $2 to north of $4 a gallon.

While he had no hard data, he's noticed two changes toward fuel economy, said Kevin Broom, spokesman for the Recreational Vehicle Industry Association in Reston, Va.

Motor home manufacturers increasingly work with the Class C Dodge Sprinter chassis, rather than the larger, thirstier Class A choices, Broom said. Makers of travel trailers have been using different materials that reduce their weight, allow for a smaller tow vehicle or put less strain on a bigger engine.

Fleetwood Enterprises (NYSE: FLE) in Riverside makes both products. The company is moving toward fuel efficiency on both fronts, managers there said.

Fleetwood combats gas-price woes on three fronts: it's using lighter materials, looking for more fuel-efficient engines and adopting more aerodynamic shapes, said Luc van Herle, product marketing manager for motor homes.

Motor homes of all sizes will be lighter and more fuel-efficient in the future, he said.

For customers willing to give up some of their space but who want all the amenities they've become used to seeing on a motor home, manufacturers will be "challenged to make the most efficient use of space we can," van Herle said.

The boating and aircraft industries have provided examples for motor home makers, he said.

The number-one priority is getting the weight of the products down, said Bob Rogers, product marketing manager for Fleetwood travel trailers. Most trailer frames have been switched from wood to aluminum, which is lighter but just as durable, Rogers said.

Fleetwood's Backpack and Compass models can be towed by a small SUV such as Ford Escape, or even a crossover vehicle such as a Ford Edge, he said.

Aerodynamics are on the minds of Fleetwood's travel trailer engineers, who have narrowed some models to seven feet in width - narrower than the tow vehicle, and therefore less prone to wind resistance.

Perris-based MVP RV hopped on the lightweight bandwagon with production of a new Coast travel trailer that weighs about 1,000 pounds less than similar-sized models.

One option that passenger vehicle owners have had for several years is a hybrid drivetrain, with an electric motor that augments a gasoline engine.

It's unlikely Fleetwood will take that approach soon, because the start-and-stop driving that recharges hybrid batteries doesn't fit with the way motor homes are used, van Herle said.

Fuel-cell technology is more likely for the RV industry, and that technology probably will be used for power generation before it's used to move the vehicle, he said.

Ultimately, the RV owner can save more fuel by changing travel plans, van Herle said.

"People are saying, 'Let's go to Big Bear instead of going up to Alaska.' "