Among the fuels tested on the SOFCs were: propane, methane, ethanol, natural gas and diesel.

Since 1999, automakers like BMW and Delphi Automotive have been looking toward SOFC technology as a promising alternative to traditional combustion engines. BMW and Delphi plan to introduce SOFC technology into automobiles as auxiliary power units hopefully in the next decade. These units would run the vehicle's electrical systems, easing the load on the engine, and allowing for smaller more efficient engines.

The most attractive feature of SOFC systems are their fuel flexibility. Because they can run on a variety of fuels, or electrolytes, SOFCs eliminate the need to provide hydrogen as a source of fuel. But being able to run on multiple widely available petrochemical fuels also frees American automakers from dependency on any one fuel in case of a shortage. Franklin Fuel Cells believes its improved SOFC technology is key in enabling smooth transition off of fossil fuels, the company has said.

The SOFC systems operate at high temperatures up to 1000 degrees Celsius. This high temperature makes it more efficient than both Proton-Exchange Membrane (PEM) fuel cells, which run on hydrogen, and combustion engines. These systems run clean and quiet, and, because they don't get poisoned by carbon dioxide, they can run on many different fuels.

PEM cells require 4 steps to convert liquid to gas fuel. In contrast, SOFC systems only require one step to remove sulfur from the fuel before it can be used. However Franklin Fuel Cells reports that its fuel cells require no reformers or de-sulfurizers. This makes for smaller, more efficient, and cheaper SOFCs.

One of the main obstacles keeping SOFC systems out of vehicles is their high operating temperatures. Warming up the fuel cell to 1,000 degrees Celsius can take around 45 minutes, and the material needed to withstand that heat is expensive. Engineers are working to lower the operating temperature under 700 degrees Celsius which would solve some of these issues, the company said.