Car firms are desperate to identify a replacement for oil, but already there seems to be confusion over which direction to follow, writes Michael McAleer

Reclining in the soft leather rear seat of a Lexus, electric motors gently massaging your back while you watch the latest Sopranos DVD, it's hard to feel you're doing your bit to save the planet.

Yet up front, as our driver hits 160km/h on the German autobahn, the five-litre V8 engine of the new LS600h petrol-electric hybrid shares the task of lugging this 2.4 tonne behemoth with a 250v electric motor.

The end result is a car that claims an official fuel economy figure at 9.3 L/100km (30.4mpg) and CO2 emissions at just 219g/km.

Neither figure will secure Green Party approbation, although they leave its direct competitors looking like planet chokers.

True, the Lexus hybrid starts at €139,000, so it's not exactly a mass market model, but the Japanese premium brand is not worried about sales. Hybrid is a global hit.

Some form of joint petrol-electric propulsion has been on offer by engineers since Ferdinand Porsche developed his Mixtewagen back in 1902.

However, it was nearly 100 years later that the Toyota Prius made its debut in 1997 (in the US initially), followed in 1999 by the Honda Insight.

At the time, few other car companies paid much attention to hybrid developments.

The main industry issue was replacing the oil dependency entirely.

Even when the second generation Prius went on sale in 2003, European and US manufacturers still dismissed it as nothing more than a marketing gimmick.

They wanted the industry to concentrate on long-term replacements for oil rather than simply reducing consumption.

However, while the cynics abounded, the power of the Toyota marketing machine got to work.

The timing could not have been better. Climate change has risen up the ranks of political and social concerns, while in the background Prius sales rocketed.

While it has had very respectable sales on European markets, in the US, where Toyota is the top-selling brand, it is now its third best-selling model.

The introduction of hybrid versions to its premium Lexus range has further expanded sales and made hybrid the established third powertrain option after petrol and diesel.

Overall sales of hybrid models from the Japanese manufacturer topped one million last June.

Toyota's competitors are now backtracking from their earlier cynicism.

At last month's Frankfurt motor show - the world's largest gathering of gleaming new cars - chief executives from the lowly new Chinese brand Brilliance to the prestige of Porsche were busy promoting their environmental advances.

The latter even introduced a new petrol-electric hybrid version of its Cayenne sports utility vehicle.

Everyone was keen to save the planet, and virtually every firm had its own catchy slogan for a green model or concept car: from Ecoflex at Opel to Econetic at Ford.

Mercedes, with its own buzzword - Bluetec - plans to have a hybrid version of its flagship S-Class on sale by 2010.

Within the next five years, every large manufacturer is expected to have some form of hybrid model on offer. The problem is hybrids do not end our oil dependency, merely cut down our consumption.

Aside from hybrids there is the current popularity of bioethanol fuels - derived mainly from sugarcane but also vegetable oils.

This offers a less polluting product from seed to wheel, but raises other challenges in terms of global land usage.

Even advocates of biofuels admit they are unlikely to be the final solution to wean us off oil.

For that, most engineers in the car industry point to hydrogen. Operated via a fuel cell that uses compressed hydrogen gas, they are effectively electric cars, but ideally with ranges that far exceed the current plug-in models on offer.

Several prototypes have been built and hydrogen is being hailed as the saviour of our motoring life.

BMW has hydrogen vehicles in its fleet - a 7-Series model that runs on either hydrogen or petrol - although it is not for public sale.

Honda boss Takeo Fukui, says he wants hydrogen models to be available in showrooms in Japan and the US by next year.

Yet for all the advocates who predict hydrogen will be the fuel source of tomorrow, there are many who predict its arrival on the mainstream will always be "tomorrow".

Cynics point to the fact Mercedes predicted several years ago that hydrogen models would be on sale by 2004.

Many engineers working on hydrogen projects predict it will realistically be another 10 to 20 years before we see mass market demand for hydrogen-powered cars.

Whatever about producing the cars, it also entails a massive infrastructural change in our fuel supply system.

In the short-term at least, the emphasis in the mainstream car market will continue to be on reducing consumption and emissions rather than replacing the entire infrastructure and power source. Hybrids and biofuels seem set to rise in popularity.

Some 128 years after Karl Benz received the patent for his internal combustion engine, it seems that for all the innovation mustered by the car industry in terms of safety, security, design and marketing, we will still be pulling up at the oil-filled fuel pumps for several years to come.

It's just that we'll feel that bit more green, even in our luxury limousines.