According to the National Ethanol Vehicle Coalition, E85 reduces greenhouse gas emissions such as carbon monoxide by as much as 39 to 46 percent, compared to gasoline. It also reduces hydrocarbon and benzene emissions. The reason is the ethanol, as its water soluble and biodegradable, thus much cleaner burning. Ethanol makes up 85 percent of E85 fuel, the remaining 15 percent being gasoline. Bottom lne: E85 is cleaner at the tailpipe than a gas-only powered engine. For those shopping for an environmentally clean car, be aware that many critics believe that the fossil fuel used to refine E85 offsets any gain you may get at the tail pipe. As the refinement of this fuel improves, look for the environmental benefits to also improve.