By John D. Stoll

LOUISVILLE, Ky (Reuters) - In America's quest for cleaner fuel, at least one major U.S. industry is holding on to the sputter and grime of the internal combustion engine.

From log splitters to snow blowers, the $15 billion outdoor power equipment industry sells tens of millions of oil-powered machines a year to U.S. landscapers, loggers, homeowners and a litany of other buyers.

While lawn mowers get faster, snow blowers cover more ground and handheld products get lighter, their propulsion has barely changed beyond getting more mileage out of gasoline.

This week, at the annual Green Industry and Equipment Expo in Louisville, Kentucky, manufacturers will once again unveil new equipment with some promise of a cleaner, greener future.

"We do anticipate the trend moving in the direction of alternative energy," said Jeff Salamon, director of marketing at MTD Products Inc. "Some customers do like the experience of being unencumbered by exhaust and gasoline."

However, the answers offered will likely be more of the same.

"Gas engines, by and large, are the most efficient way to go," Briggs & Stratton Corp Chief Executive Todd Teske told Reuters in an interview shortly after a press conference to unveil the company's latest engine. Briggs & Stratton sells electric mowers, but only in Australia.

NOT YOUR FATHER'S MACHINE

For decades, garden and snow machines were a poster child for harmful emissions. In fact, when auto executives were confronted by regulators for their contributions to pollution, they pointed to the lawn industry as a more offensive culprit.

In the mid-1990s, that began to change as the Environmental Protection Agency began pressuring engine makers with tougher standards.

"These aren't your father's lawn machines," Kris Keiser, president of the Outdoor Power Equipment Institute, said.

At Briggs & Stratton, for example, Teske said emissions have been cut by 75 percent since the mid-1990s thanks to manufacturing upgrades and design improvements. Another 35 percent reduction will come in 2012.

The auto and other industries are under constant pressure to raise fuel economy or tap new technologies because their customers often burn through dozens or more gallons of gasoline each month. As gas prices rise, so does the strain on pocketbooks.

But outdoor equipment users don't face these pressures.

"People who use our products typically use no more than five gallons of gasoline per year," Keiser said. This lessens the likelihood that customers will demand huge advances in fuel economy or solutions that lessen their operating expenses.

Even commercial landscapers here in Louisville do not seem to be budging, despite high weekly fuel costs.

"THIS CUSTOMER IS DIFFERENT"

Wang Xiaoguang, general manager of Wenling Leo Garden Machinery Co -- which claims to be the largest exporter of Chinese garden machines -- is learning this lesson first hand.

Standing at his exhibition booth, he talks about Leo's successful business of exporting electric mowers to Europe.

"This customer is different," Wang said of the U.S. market which Leo has yet to crack. "They have different standards."

But some companies, including a handful of start-ups, aren't waiting for customers to change their minds.

Lincoln Jore, a 28-year-old entrepreneur from Ronan, Montana, launched a new "GasLess" outdoor equipment company called Core Outdoor Power on Thursday aimed at commercial landscapers and higher-end homeowners.

His first product, a $249 weed whacker weighing 11 pounds, is powered by an unconventional motor and lithium-ion battery that slips in and out of the machine so it can be charged on a separate dock. It will begin appearing at independent U.S. dealers early next year.

The "market has missed the mark on developing alternative energy products that meet performance expectations," he said.

By 2013, Jore plans to have a broader range of products, including a lawn mower and leaf blower that don't use gas.

TWICE THE PRICE

But even the most established global players are finding it hard to turn the tide.

Honda Motor Co sells thousands of hybrid snow blowers in Japan annually and is bringing a hybrid model to the United States. This model promises to be the Cadillac of its class, capable of clearing 83 tons of snow in an hour and sweep a city sidewalk in one pass.

But, at $8,000, this machine is twice as expensive as the company's previous top-of-the-line model, and hybrid technology is driving up the cost. Honda's expectations for sales of the Japan-built hybrid are extremely modest, but it wants to test the market before committing to other alternative-energy models.

If Wisconsin-based Ariens Co's experience during last year's tough winter is any indication, there may be hope for Honda. Ariens put on sale an electric snow blower priced 60 percent higher than a conventional model. The company sold out of its limited quantity of electric snow blowers amid heavy snowfall and tight industry capacity.

Stihl Inc, which says it is the No. 1 seller of handheld outdoor power devices, is also branching out. It has a new lineup of chainsaws, leaf blowers, weed whackers and hedge trimmers that are powered by lithium-ion batteries.

The products cost 30 percent more than conventional gas-powered versions and, while initial demand has outstripped expectations, the company said it is too early to break out specific sales results.

Cub Cadet, a brand owned by MTD, has a lithium-ion-powered product line on display similar to those sold by Stihl, but demand so far is only from a "faction" of customers, Salamon said.

Still, Cub Cadet is poised for a shift at some point, even if it is slow going, he noted.

(Editing by Richard Chang)