[vatdevil]

Its the RVP (Reid Vapor Pressure) number that matters. Lower is better, in the case of carbs and heat. Winter gas is around 13.5 Summer is either 9 or 7.8 in most areas. VP110 is 6.7 which is why blending some into pump gas helps. The EPA mandated numbers are on a sliding scale, dropping in the spring and rising in the fall.
If the supplier splash blends in ethanol, they are granted a 1 PSI waver. Winter limit is then 14.5 and summer 10 or 8.8. This is why ethanol free gas may help a bit.