How many types of unleaded fuel does the EPA require to be made?

Question

My professor says that different environments require many different types of mixtures to be made depending on the area. How can I find this information?

Answer 1

The US EPA with perhaps best of intention has made it very hard for gasoline makers to produce the a fuel that can be used anywhere in the US.  

Check the US EPA regulations in this regard and you will see how it varies.

Answer 2

there is roughly 45 - 50 special blends and that is just for the states  each region has different requirements  for each season