Flexible Fuel Vehicles

A flexible-fuel vehicle or dual-fuel vehicle is an automobile that can typically alternate between two sources of fuel. A common example is a vehicle that can accept gasoline mixed with varying levels of ethanol (gasohol). Some cars carry a natural gas tank and one can switch from gasoline to gas.

Flexible-fuel vehicles in the United States

North American vehicles from approximately 1980 onward can run on 10% ethanol/90% gasoline (e.g., E10) with no modifications. Prior to 1980, many cars imported into the United States contained rubber, aluminium, and other materials that were generally non-compatible with any ethanol in their fuel delivery systems, and these cars experienced problems when E10 was first introduced.Cars made in the US from the late 1970's onward can run on E10 with no modifications. E10 fuel is widely available. Going beyond 10% ethanol generally requires special engineering.

In the United States, many flexible-fuel vehicles can accept up to 85% ethanol (E85) or up to 85% methanol (M85). The fuel mixture is automatically detected by one or more sensors, and once detected, the ECU tunes the timing of spark plugs and fuel injectors so that the fuel will burn cleanly in the vehicle's internal combustion engine. Originally, sensors in both the fuel-line and in the exhaust system were used for flexible fuel vehicles. In recent years, manufacturers have instead opted to use only sensors in the exhaust manifold, before the catalytic converter, and to eliminate the fuel inline sensor. As E85 and M85 are more corrosive, special fuel system materials are also required. Some manufacturers also require a special motor oil be used, particularly in vehicles using methanol fuel.

In 1993 through 1995, Chrysler offered M85 flexible-fuel versions of the Dodge Spirit and Plymouth Acclaim with an MPFI 2.5 L 4-cylinder engine. FFV Chrysler minivans were also offered beginning around the same time, with a version of the corporate 3.3 L V6 enigne. In 1998, General Motors Corporation introduced their first light truck (an S10, with 2.2L engine) in a flexible-fuel configuration. In 1999, Ford Motor Company introduced a flexible-fuel option on its Ford Ranger pickup trucks, and it has also been an option on the company's Taurus model. Other manufacturers such as Mercedes-Benz also offer E85/Flexible fuel vehicles. Flexible fuel vehicles are often identified as such by exterior badging. They can also be identified by labelling adjacent to the fuel filler and fuel gauge, and by the engine identifier digit in the VIN.

As of 2005, most existing vehicles that are available to the public with flex-fuel engines are sport-utility vehicles or others in the "light truck" class. Sedans, wagons, and others are usually only available in flexible-fuel configurations as part of fleet vehicle purchases by companies. Starting in 2006, though, more widespread availability is planned for standard models intended for non-fleet sales.

A 1988 federal law provides an incentive for creating flexible fuel vehicles in the form of credits that can be used to relax Corporate Average Fuel Economy fuel efficiency standards. It is alleged that this efficiency relaxation has decreased overall US fleet efficiency, thereby resulting in increased nationwide fuel consumption.[1]

Over 4 million flexible-fuel vehicles are currently operated on the road in America, although a 2002 study found that less than 1% of fuel consumed by these vehicles is E85[2].

Flexible-fuel vehicles in Brazil

Since the oil crisis in the 70's, Brazil has been selling ethanol as a fuel. Car manufacturers modified gasoline engines so as to better support alcohol characteristics (mainly changes in compression ratio and better robustness to protect from corrosion) and have been selling ethanol powered cars since then, in a lower scale than gas-powered cars. However, flexible fuel technology started to be investigated only in the 1990s. The flexible fuel car is built with an ethanol engine, a lambda probe to measure the mixture of gases that leaves the engine and a controller that regulates the input of fuel and the spark time, so as to correct the quality of the mixture. Those cars can run with arbitrary combinations of gasoline and alcohol (up to 100% of alcohol), but current engines cannot use pure gasoline - they are designed to run on gasoline mixed with 20% to 25% of ethanol, which is obligatory in Brazil.

In May 2003 Volkswagen built for the first time a production flexible fuel car, the Gol 1.6 Total Flex. Chevrolet followed two months later with the Corsa 1.8 Flexpower, which is named Celta in Brazil. The first compact car with flexible fuel engine was the Astra 2.0 Flexpower, and mid-size cars, minivans and pickup trucks followed later. As of 2005, popular manufacturers that build flexible fuel vehicles are Chevrolet, Fiat, Ford, Peugeot, Renault and Volkswagen. Flexible fuel cars were 22% of the car sells in 2004, 53% in 2005, and 75% and 90% rates are estimated for 2006 and 2007.

There's another type of flexible fuel vehicle that is not uncommon in Brazil. Those are the cars able to switch from gasoline to natural gas. The term "flex-fuel", however is never used to describe those cars; instead, they are called bi-fueled vehicles or tri-fueled if they are built with an ethanol-gasoline flexible fuel engine (and tetra-fueled if they can run on pure gasoline). These vehicles are always adapted in specialized houses after they are bought. In many cities, natural gas shares a small part of the fuel market with gasoline and ethanol. It has the advantage of being the cheaper fuel in the country and the disadvantage of having the lowest mileage and taking a lot of space in the trunk.

Trucks are diesel powered and there's no provision to convert them to flexible fuel vehicles. Instead the trend is to slowly replace diesel with bio-diesel. The currently allowed mixture is 98% diesel and 2% bio-diesel. The mixture of 95% diesel and 5% bio-diesel will become a requirement only in 2013.

Flexible-fuel vehicles in Europe

For a long time Ford Taurus was the only flexible-fuel vehicle sold in Sweden. It was later replaced by Ford Focus. In 2005 Saab began selling its 9-5 Biopower, and Volvo its S40 and V50 with Flexifuel engines. There are also plans of selling E85 fuel, and then some flexible-fuel vehicles, in other European countries.

List of currently-produced flexible fuel vehicles

Europe

• Ford Focus, Focus C-MAX
• Saab 9-5
• Volvo S40, V50

USA

• Chrysler Sebring
• Dodge Caravan, Durango, Grand Caravan, Ram Pickup, Stratus
• Ford Crown Victoria, F-150, Grand Marquis, Taurus
• Chevrolet Avalanche, Silverado, Suburban, Tahoe, Impala, Monte Carlo
• GMC Sierra, Yukon, Yukon XL
• Nissan Titan

Brazil

• Chevrolet: Celta, Classic, Corsa, Astra, Vectra, Montana, Meriva, Zafira
• Citroën: C3
• Fiat: Mille, Palio/Siena/Strada, Doblò, Idea, Stilo
• Ford: Fiesta, EcoSport
• Peugeot: 206
• Renault: Clio, Mégane, Scénic
• Volkswagen: Gol, Fox, Kombi

See also

• Worldwide Flexible-Fuel Vehicles
• Plug-in hybrid electric vehicle
• Southern Grease - A great beginner's tutorial on using renewable fuel in diesel engines