Propane:liquefied petroleum gas (LPG)

       Propane or liquefied petroleum gas (LPG) is a clean-burning fossil fuel that can be used to power internal combustion engines. LPG-fueled vehicles produce fewer toxic and smog-forming air pollutants. LPG is usually less expensive than gasoline, and most LPG used in U.S. comes from domestic sources.
No LPG-fueled light-duty passenger cars or trucks have been produced commercially in the U.S. since the 2004 model year, but gasoline and diesel vehicles can be retrofitted to run on LPG in addition to conventional fuel. The LPG is stored in high-pressure fuel tanks, so separate fuel systems are needed in vehicles powered by both LPG and a conventional fuel such as gasoline.

 Advantages:      

• Fewer toxic and smog-forming air pollutants
• 85% of LPG used in U.S. comes from domestic sources
• Less expensive than gasoline

 Disadvantages:

• No new passenger cars or trucks commercially available (vehicles can be retrofitted for LPG)
• Less readily available than gasoline & diesel
• Fewer miles on a tank of fuel

Hydrogen Fuel:
Hydrogen (H₂) is being aggressively explored as a fuel for passenger vehicles. It can be used in fuel cells to power electric motors or burned in internal combustion engines (ICEs).
It is an environmentally friendly fuel that has the potential to dramatically reduce our dependence on imported oil, but several significant challenges must be overcome before it can be widely used.

Benefits

Produced Domestically. Hydrogen can be produced domestically from several sources, reducing our dependence on petroleum imports.
Environmentally Friendly. Hydrogen produces no air pollutants or greenhouse gases when used in fuel cells; it produces only nitrogen oxides (NOx) when burned in ICEs.

Challenges

Fuel Cost & Availability. Hydrogen is currently expensive to produce and is only available at a handful of locations, mostly in California.
Vehicle Cost & Availability. Fuel cell vehicles are currently far too expensive for most consumers to afford, and they are only available to a few demonstration fleets.
Onboard Fuel Storage. Hydrogen contains much less energy than gasoline or diesel on a per-volume basis, making it difficult for hydrogen vehicles to go as far as gasoline vehicles between fillups—about 300 miles. Technology is improving, but the onboard hydrogen storage systems do not yet meet size, wieght, and cost goals for commercialization.
Other challenges include fuel cell performance, customer acceptance, and hydrogen transport and bulk storage.

Ethanol is an alcohol-based fuel made by fermenting and distilling starch crops, such as corn. It can also be made from "cellulosic biomass" such as trees and grasses. The use of ethanol can reduce our dependence upon foreign oil and reduce greenhouse gas emissions.

E10 (gasohol)

E10 (also called “gasohol”) is a blend of 10% ethanol and 90% gasoline sold in many parts of the country. All auto manufacturers approve the use of blends of 10% ethanol or less in their gasoline vehicles. However, vehicles will typically go 3–4% fewer miles per gallon on E10 than on straight gasoline.¹

E85

E85, a blend of 85% ethanol and 15% gasoline, can be used in flexible fuel vehicles (FFVs), which are specially designed to run on gasoline, E85, or any mixture of the two. FFVs are offered by several vehicle manufacturers. To determine if your vehicle can use E85, consult your owner’s manual or check the inside of your car's fuel filler door for an identification sticker.
Cost. Cost varies regionally. It is cheaper than gasoline in some areas, such as the Midwest, and more expensive in others.
Availability. More than two thousand filling stations in the U.S. sell E85, and that number is increasing rapidly. Visit the Alternative Fueling Station Locator for locations of service stations selling E85.
Performance. No noticeable difference in vehicle performance when E85 is used.
MPG. FFVs operating on E85 usually experience a 25–30% drop in miles per gallon due to ethanol’s lower energy content.²

Advantages of E85:

• Domestically produced, reducing use of imported petroleum
• Lower emissions of air pollutants
• More resistant to engine knock
• Added vehicle cost is very small

Disadvantages of E85:

• Can only be used in flex-fuel vehicles
• Lower energy content, resulting in fewer miles per gallon
• Limited availability
• Currently expensive to produce

Diesel Vehicles

Diesel vehicles may be making a comeback. Diesel engines are more powerful and fuel-efficient than similar-sized gasoline engines (about 30-35% more fuel efficient). Plus, today's diesel vehicles are much improved over diesels of the past.

Better Performance

Improved fuel injection and electronic engine control technologies have

• Increased power
• Improved acceleration
• Increased efficiency

New engine designs, along with noise- and vibration-damping technologies, have made them quieter and smoother. Cold-weather starting has been improved also.

Cleaner

Today's diesels must meet the same emissions standards as gasoline vehicles. Advances in engine technologies, ultra-low sulfur diesel fuel, and improved exhaust treatment have made this possible.
Although emissions of particulates and smog-forming nitrogen oxides (NOx) are still relatively high, new "clean" diesel fuels, such as ultra-low sulfur diesel and biodiesel, and advances in emission control technologies will reduce these pollutants also.