Despite the focus on developing and promoting environmentally friendly engine types, 69 percent of vehicles globally will still run on conventional gasoline in 2015, say industry analysts Frost & Sullivan.

Of those, 26 percent of vehicles are likely to use diesel, while only about 6.0 percent will be gas-electric hybrid vehicles, the company predicts.

Gasoline vehicles will tend to predominate in major automotive markets such as North America and Japan, though hybrid vehicles will also gain popularity in both regions, researchers think. Diesel engines will establish a strong presence in Europe and India, with their market share in India set to grow from 29 percent in 2005 to 50 percent by 2015, they say.

Alternative fuel vehicles will also gain market share as the global focus on reducing emissions increases. The number of these vehicles will increase to 3.0 million worldwide by 2015, with ethanol and natural gas vehicles expected to be the most prominent among them, they predict.

Advanced valvetrain technologies such as variable valvetrain (VVT) are fast gaining in popularity and look set to displace conventional fixed timing systems for gasoline vehicles. Global penetration rates of these technologies will reach 25 to 30 percent by 2015.

"Complying with stringent emission norms and offering increased fuel savings and better performance are some of the important factors that vehicle manufacturers and suppliers are working towards in terms of powertrain," said Frost & Sullivan Senior Research Analyst Vijayendra R. Rao.

"There is a definite trend toward advanced valvetrain systems for gasoline engines, increased penetration of direct injection for gasoline vehicles, engine downsizing and turbocharging."

Rao's forecasts are made in Strategic Analysis of Global Markets for Engine Technologies, available only to Frost & Sullivan's automotive coverage subscribers.