For Dan Norte, deciding where to fuel up his Ford F150 pickup is not always as simple as scanning pump prices. When he heads to Iowa to see family, the synthetic-oil dealer from Owatonna, Minn., burns an 87-octane Minnesota-mandated gasoline blend that is 10 percent corn-based ethanol. It costs about the same as comparable-grade gasoline.
For the trip back he has a 15-percent option, an Iowa blend rated at 89 octane that can be up to a nickel a gallon cheaper. But Mr. Norte has figured out that his savings would probably be erased by lost m.p.g. from the faster-burning fuel.
With energy independence increasingly cast as a matter of national security, and the doubling of biofuel output by 2012 mandated by last summer's energy bill, plenty of other Americans are finding more cause for making complex calculations that involve alternative fuels.
Some 90 percent of 1,000 voters surveyed last month by the nonpartisan Energy Future Coalition in Washington supported the notion of having one-quarter of US energy demand met by renewables by 2025.
"We have a new reality," says Ron Cogan, editor of the Green Car Journal in San Luis Obispo, Calif. "And I think that's changing the way people look at the vehicles they want to buy and operate on a daily basis."
"Two years ago, it looked like the alternative-fuels business was going to atrophy," says Fred Mayes, who tracks renewable-fuel data for the Energy Information Administration, a quasi-independent arm of the Department of Energy. "There was no interest, no direction, no incentives, no major breakthroughs. It was stuck in low gear."
Barriers still exist, including not enough filling stations and a projected shortfall of ethanol production that will contribute to higher gas prices this summer, many experts say.
Still, energy remains in an evolutionary mode. Mr. Mayes says government analysts trying to make projections can barely keep up with all the emerging options. As gas-electric hybrids fill a gap, and hydrogen fuel cells remain a holy grail, old-school combustion engines show signs of hanging on - and leaving fewer smudges - because of what they can burn.
That has alternative-fuel vehicles merging out of the slow lane for the near term - and consumers facing more signposts than they can easily read.
"There are so many balls up in the air," says Mayes. Consider: Biodiesel made from soy or other forms of biomass; cellulosic ethanol, derived from corn husks and other organic waste rather than corn; E85 ethanol that's only 15 percent gasoline; even "petro" diesel that burns cleaner than the diesel used in the smoke-belching cars many Americans recall - and that is made cleaner still by exhaust-treatment technologies like DaimlerChrysler's BlueTec, announced last month.
Mayes has just returned from a conference at which he heard of a new "biomass gasification" technology that "can produce ethanol cheaply in huge quantities from trash, coal, wood, switchgrass - anything you name that has carbon in it," he says.
Don't expect a federal decree favoring sales of one fuel, like the legislation of unleaded in the 1970s, experts say. If anything, Washington might step back and let automakers go nose-to-tailpipe with states. A federally sponsored panel (the National Academies' National Research Council) this month strongly urged that states should have the power to follow California's lead in adopting emissions standards tougher than the federal ones.
Many automakers have several horses in the alt-fuels race. Perennial innovator Honda - a leader, with Toyota, in hybrids - also has its hydrogen FCX and its natural-gas-powered Civic GX, "the cleanest internal-combustion ever," Mr. Cogan says.
GM, which has pushed ahead with hybrids, has also ramped up marketing for flexible-fuel vehicles that can run on either straight gasoline or E85. It sold 270,000 E85-ready vehicles in 2005, says Sherrie Childers Arb, director of environment and energy communications at GM, and estimates it will sell 400,000 this year.
The main gains: fewer pollutants and a tilt toward a domestic, renewable resource. But note: Experts say costs associated with ethanol remain, for now, too high to provide workable margins for anyone in the sales chain.
"We're not suggesting that you'll replace all gasoline with E85 ethanol," says Ms. Childers Arb. "We continue to believe that a lot of technologies and alternative fuels will coexist in the marketplace of the future."
In fact, "none of the alternative fuels currently on the horizon have a chance of replacing gasoline anytime soon," says Jim Motavalli, author of "Forward Drive" (2004). He cites, among other limitations, insufficient agricultural production for biofuels to make a dent in fossil-fuel consumption.
Mr. Motavalli also hopes carmakers will keep tweaking other factors, such as composite materials that reduce weight but still provide safety. "One trend that I see in hybrids is very regrettable," he says. "That's the trend toward hybridizing bigger and heavier luxury cars with the advantage being that they have more performance."
He urges car shoppers to inquire about PZEVs, partial-zero-emissions vehicles. Now on the market in many states, PZEVs are cleaner editions of gasoline models - Toyota Camrys, BMW 325s - that cost a few hundred dollars more. "Something like 20 manufacturers make them," Motavalli says.
Whichever way the alt-fuel road goes, potholes lie ahead.
"There are always unintended consequences," says Cogan. If demand for farmed biomass surges, for example, questions will arise: Should crops be expended as fuel or used to feed the world? "You just need to think ahead," he says.
Certain to push progress: rising stakes. The global market for biofuels hit $15.7 billion last year, says Clean Edge, a Portland, Ore., research firm. In a decade, it could be $52.5 billion.
"At some point" says Cogan, "we will move on from the age of oil."
Until the alternative-fuel shakeout is complete - a process driven by technology, legislation, incentives, and reaction to consumer demands - don't expect to see gasoline go away.
Perhaps not for decades.
"In the case of almost every alternative fuel, the supply is not there," says Ron Cogan, editor of the Green Car Journal. "There are 176,000 gas stations in the country. There are probably 600 biodiesel stations, 500 ethanol stations, [though] these numbers change daily."
Here's a distillation of what experts say about some of the main alt-fuel contenders:
'Clean' diesel. Still largely a European phenomenon, it's a combination of higher-grade fuel and car-design changes, such as DaimlerChrysler's BlueTec exhaust technology. Diesels inherently get about 30 percent more miles per gallon than gas vehicles. Some alt-fuel watchers predict a lightweight, 150 m.p.g. clean-diesel car by 2009.
Ethanol. Primarily corn-based, it runs the gamut from a 10 percent gasoline additive (gasohol) that works without engine modification to E85, just 15 percent gasoline, which works in flexible-fuel vehicles. An ethanol variation, cellulosic ethanol, uses corn husks and other crop waste. Experts caution that a production shortfall will raise pump prices this summer.
Biodiesel. Not yet widely produced commercially, this biofuel option (made, for example, from soy) is coming on strong. It's already mandated by some Midwestern states, blended with conventional diesel. Advances have reduced filter-clogging and cold-flow issues. (Like diesel, biodiesel tends to jell at low temperatures.)
Natural gas. This clean-burning option calls for frequent refills, which limits range. Home garages can be built with refilling stations, but retrofitting an existing garage can be costly. Compressed natural gas is seeing some use with fleets; larger vehicles can carry higher-capacity tanks.
Hydrogen. Widely seen as the eventual winner, probably in fuel-cell form, hydrogen carries inherent complexities: It's light and tends to leak out of containment areas, and it is highly combustible. Early uses include a bus fleet in the San Francisco Bay area.