I know that they are not the exact same, but they can't add "other ingrediants" not listed in the MSDS...

Quote from the website listed above:
http://www.zhome.com/ZCMnL/PICS/win.../winterGas.html

"Here's the poop: As specified by state law, reformulated winter gas contains any number of lighter, lower-boiling-point hydrocarbons (butane, propane, etc.) that just so happen to have an excellent octane value. Added to this may be any number of oxygen-bearing ether compounds (MTBE, ETBE, ethanol) that improve emissions and also have a relatively high octane blending value."

The MSDS has a value range to cover differences in the manufacturing process, but additional hazardous chemicals cannot be added without making their way onto this label. Thus, there would be different MSDS for different times of year if they were adding other compounds to the fuel. I can see manipulating the quantities of what's there, but as far as adding anything else, I doubt it. Not saying it isn't possible...

 

That's basically it. Remember, gas isn't defined so much by exactly how much of this or that is in it, but by its properties. Of course there are minimums for some things (e.g. O2) and maximums for others (e.g. benzene). The exact formulation of a batch of gas is whatever they could get out of the refinery the cheapest that meets the specs from the crude they started with (and given the demand for other product streams).

Dave

 

I saw about a 1-3mpg improvement with the cams. I average 22-24 mpg with frequent highway pulls.