Most automobile executives attending the 2005 Frankfurt International Auto Show agree that world has reached the Era of Diminishing Returns in crude oil production.

Most are worried about the eventual effects of globally soaring motor fuel prices, especially in Europe, where heavily taxed gasoline has pumped costs up to the U.S. equivalent of $6 a gallon in Germany and close to $7 a gallon in France.

And although many leaders in the automobile industry have played down, or even ridiculed, charges that their cars and trucks are major contributors to global warming -- a climatic aberration blamed and credited for all kinds of natural disasters -- the evidence here is that they now are willing to admit that environmentalists, many as manic as Cassandra in her dire pronouncements, may have a point.

In all of the exhibition halls on the sprawling Frankfurt/Main Trade Fair Grounds, automotive manufacturers have given as much attention to vehicular potential for smog-forming carbon dioxide as they have to performance staples such as horsepower and torque. In the case of CO2, less is best; and how much less is shown prominently on the information sheets on all cars and trucks presented.

Yet, altruism remains a timid challenger to market opportunities and realities. As a result, much of what is on display gives the impression of an industry of multiple personalities -- reaching out to environmental forces, such as Germany's Green Party, with one hand while selling as much horsepower and grabbing as much cash of any available color with the other.

And so we have Mercedes-Benz rolling out its 6.3-liter, 510-horsepower V-8 ML63 sport-utility vehicle for the international automotive media, while loading up its displays in its huge multilevel exhibition center here with models such as the B-Class wagon, a fuel-efficient, compact urban runner that won't be coming to the United States anytime soon.

Latest examples of the Mercedes-Benz-owned micro Smart cars are also to be found. With diesel engines, those teeny automobiles can get as much as 60 miles per gallon; and they are easy as heck to park in congested city environments. But, alas, Mercedes-Benz officials confirmed here last week that the company's on-again, off-again introduction of the Smart car in the United States is off again -- at least until the end of 2006, if not forever.

It seems that the company is having a hard time making a business case for taking the Smart to America, either as the Smart Fortwo two-seater or as the Forfour sedan. But it has no qualms about the stateside introduction of the ML63, or the newest version of its fleet-leading S-Class -- the 2007 S-Class, with multiple engine options including a 338-horsepower V-8 and a 570-horsepower, twin-turbo V-12 for people who have considered suicide when a V-8 wasn't enough.

But along with that extravagance, Mercedes-Benz also has announced new energy-conservation initiatives, including the near-term introduction of what it calls "Direct Hybrid" vehicles that will employ a 3.5-liter V-6 engine working in tandem with a compact, high-torque electric motor to improve fuel efficiency by as much as 30 percent to help further reduce tailpipe emissions. A diesel hybrid power system, dubbed "Bluetec Hybrid" by Mercedes-Benz also is heading to market.

General Motors Corp. remains the world's largest automotive manufacturer; and a review of that company's global offerings reveals a similar-seeming product contradiction.

At one stand, GM is showing its new smaller, but still-rugged, Hummer H3 sport-utility vehicle, which gets close to 20 miles per gallon on the highway using regular unleaded gasoline. That's much better than the barely 10 miles per gallon attained by the larger Hummer H2 and the less-than-10-miles per gallon gotten by the lumbering H1.

You'd think that consumers here would gag over that sort of thing. Instead, scores of them have been lining up at the show to be photographed with the Hummer H3.

But GM isn't silly enough to believe such show-floor behavior will translate to huge sales in an economy where people are upset over just about everything -- rising unemployment and fuel prices, higher taxes and the export of good manufacturing jobs from Germany to Alabama, Mississippi, Tennessee and other low-wage areas of the United States.

GM, too, is joining DaimlerChrysler AG, maker of Mercedes-Benz cars and trucks, in the development of advanced gas/electric and diesel/electric hybrid engines. GM is offering small cars aplenty, including premium models such as the truly neat, but European-only, Cadillac BLS; and an array of attractive, fuel-efficient small wonders, such as the 2006 Opel Astra Twintop convertible with a retractable hardtop roof, the Opel Meriva and Zafira urban wagons; and micro-cars such as the Chevrolet Kalos and the funky little Chevrolet Matiz that gets in excess of 50 miles per gallon and can be parked in the very tightest of city parking spaces.

It all seems a bit crazy, disconcerting. But the car executives insist that it's just a matter of smart marketing -- aiming specific products at specific audiences in specific regions, going after as many sales as possible as many different ways as possible wherever they can be found.

Unchanged in that approach is a mind-set that will, for the foreseeable future, keep a bunch of nice little small cars out of the United States. Incredibly, both foreign and domestic automobile manufacturers are holding fast to the belief that Americans, although now paying more than $3 a gallon for regular unleaded gasoline, remain hostile to the idea of driving small cars.

The diesel-engine Cadillac BLS, available only in Europe, was presented at the International Motor Show in Frankfurt, Germany, on Tuesday.