Vapor lock- additive?

I've always used Lucas ethanol treatment in my Duster and D200, they run a bit smoother with it and aren't as prone to boiling the gas in the carb on hot days in traffic. I drive them 1-2 times a week though and they generally get filled up once or maybe twice a month. I also use it in the gas for my riding mower and that stuff lasts several months in a sealed container, just regular 87-octane E-10 pump gas.

Sta-bil 360 seems to work too, I haven't been seeing the Lucas as much in stores lately I might order some off the web.