Planned Hybrid Car Engine Combines Gas and Diesel for Maximum Efficiency
 

Diesel and gasoline are both great fuels from a chemical standpoint, each with its own unique advantages. Diesel burns more completely, lubricates the engine better, produces less carbon monoxide, and is safer as it does not produce as much flammable vapors. However it has its disadvantages -- older engines can have a greater danger of incomplete combustion, overall engine power is a bit lower, and diesel engines weigh more.

Gasoline on the other hand burns faster and produces more power (due to the faster burn, not the energetic content). However, it also typically yields worse gas mileage than diesel, combusts less completely (in well-maintained engines), usually requires a spark to ignite, and produces more pollutants and flammable vapors.

http://www.dailytech.com/Planned+Hyb...ticle15878.htm