With oil prices near $140 a barrel, motorists are starting to look seriously at both alternative fuels and electric vehicles as a way to keep driving.
But experts say it will take five to 10 years for these alternatives to take root.
In the meantime, car and parts makers, oil companies and even electricity generators are left guessing which way motorists will turn and what technology will win.
"We don't know at the moment whether it's battery-based electricity technology or sustainable bio-fuels that will be successful," said James Smith, chairman of Shell UK Ltd, speaking at a climate change seminar hosted by Reuters.
A range of options will emerge as motorists pick between 'plug-in' electric cars, longer-range gasoline-electric 'hybrids', or simply downsized, more efficient gasoline and diesel models, and as governments, worried by global warming and energy security, give more or less support for biofuels.
Hybrid vehicles, which have both a conventional internal combustion engine and electric motor and battery, are already popular. In a hybrid, the electric battery and motor aid stop-start city driving, while the gasoline engine allows longer trips, together cutting energy use and carbon emissions.
Electric car developments hinge on batteries which are light but pack enough power to travel more than 100 miles (160 km).
Alternatively, you can keep your car but switch the fuel, up to a point. Sugar-based biofuels are making serious headway against gasoline in Brazil, where nearly 90 per cent of new cars have flex-fuel engines, which burn any combination of the two.
But biofuels made from crops such as corn aren't the near-term replacement for gasoline, either. A finite supply of farm land has pitted them against food, inflating grain prices.
A tank of standard, US corn biofuel blend, called E10, contains enough calories to sustain an adult man for 11 days. That underlines the problem of using food to make car fuel while 850 million people in the world are hungry.
Sustainable biofuels from algae or woodchips that don't compete with food, may reach 10 per cent of US road fuel by 2022.
Cars fueled by hydrogen fuel cells, which rely on the conversion of hydrogen and oxygen into water and which don't have harmful emissions, are promising, but the technology is still in its infancy.