inspector1 - why is using gasoline from summer without the oxygenates a bad idea?

Yes, I have noticed too that in the winter the gas milage goes down. It is consistent, since oxygenated fules are partially oxidized or burned so they do not have the same caloric energy as plain hydrocarbon, therfore you use more fuel. Now if you use more fuel does the HC emmision go up?

I did go to the EPA website and all I could find is oxygenates is used to reduce CO emmision in winter time. I could not find the effect of oxygenates on other emissions such as HC or NOx. My car's CO emmision is 0.28 for max of 0.50 it is well below the limit. If oxygenates increase HC emission then certainly reducing the oxygenates content in gasoline will have the right effect for my situation.