Surveys of owners of hybrid powered automobiles show that on the average, each is saving about 408 gallons of fuel a year -- or, based on recent gasoline prices, about $900 annually.

That's according to surveys of almost 1,000 people by Carnegie Mellon University engineering, science and public policy students. The results were released yesterday.

The surveys also showed that owners of about 200 diesel-powered cars are saving 388 gallons of fuel each year even though they drove 22 percent more miles than they had in the past.

By comparison, hybrid owners experienced only a modest change in the amount of driving that they did, the study said. That could be because fewer hybrid owners apparently use their cars as primary vehicles.

There was a clear difference between owners of hybrids and diesels, said Scott Matthews, an assistant engineering and public policy professor. "The diesel owners tended to be gear heads who wanted to drive quite a lot, and weren't as concerned about fuel and emissions issues. But the hybrid owners were more concerned about environmental concerns and saving fuel."

The surveys were done as part of class projects which ranged from measuring consumer attitudes toward energy efficient vehicles to developing of an interactive computer-based air emission model.