Hot and Cold Fuel Volatility Indexes of French Cars: A Cooperative Study by the GFC Volatility Group

In 1977 car manufacturers and petroleum laboratories joined to form the GFC volatility group with the objective of evaluating the sensitivity of the French car population to fuel volatility in hot and cold conditions.

After having defined a suitable test method, carrying out a similar action to the CEC CF24 activities, cars and fuels were chosen to obtain the necessary information. Twenty five cars representing approximately forty percent of the current car population were tested in 1979-80-81. Fuels were made according to a statistical plan in order to minimize the test time, with the objective of evaluating car performance with characteristics like RVP-E70 and E100. Hot tests have shown that on the average, cars respond to the already known Fuel Volatility Index (RVP + 7. E70). In the same way, cold tests put into evidence what could be defined as a “cold” Fuel Volatility Index (RVP + 22.E100). The data obtained in both types of tests allow each participant to apply his quality criteria and to obtain satisfaction curves, examples of which are shown. During 1982 and 1983, ten more cars were tested with conventional and oxygenated fuels showing that, on the average, overall performance remains the same for a given volatility. The comparison of two different rating systems was investigated, pointing out that one must be careful when defining the respective influence of each driving period (acceleration, cruise, starting and idling).