Dear EarthTalk: I understand that Toyota is planning to sell a plug-in Prius that will greatly improve the car's already impressive fuel efficiency. Will I be able to convert my older (2006) Prius to make it a plug-in hybrid vehicle? -- Albert D. Rich, Kamuela, Hawaii
Toyota is readying a limited run of a plug-in Prius, which can average 100 miles per gallon, for use in government and commercial fleets starting in 2009. Toyota will monitor how these cars, which will have high-efficiency lithium-ion batteries that haven't been fully tested yet, will hold up under everyday use.