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The new system will use more high-speed driving, partly in 20-degree cold. Air conditioning will be on some portion of each driving cycle, and there will be more stop-and-go and rapid-acceleration driving. The mileage for gas-electric hybrids probably will be 20% to 30% lower than present estimates for city driving and 10% to 20% lower on the highway. These vehicles quickly lose their all-electric advantage when operated in cold weather or quickly accelerated, Wehrum said.
Said By Aron Schatz
The Prius will drop about 10MPG total.