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Keith Park wrote: >Ok, How come then, when I park my car in the hot sun all day when its 95F >out, isn't the gas boiling in the tank when I go to drive home? > > It very well may, but a few other mitigating factors come into play: Your tank is in the shade so it's generally cooler than ambient temperature. It is under greater than atmospheric pressure because the fuel is vaporizing, which also raises the boiling point. Some of this pressure is being relieved by the ventilation system. This vapor is also condensing against the walls of the tank, continuing the cycle. Since the tank is relatively well sealed your fuel isn't going to all boil away. Because gasoline is a volatile organic compound, the molecules have a relatively weak affinity to each other- unlike water, which have positively charged and negatively charged ends that attract each other very well. This is part of the reason why boiling water is much more violent affair than boiling gasoline. Ever notice how working with gasoline on a warm day makes for more fumes than working on a cold day? I could barely smell the gasoline in the fuel tank of my Passat when I changed the fuel pump- it was 40 degrees in my garage. When I changed the fuel filter a few weeks earlier, it was an unseasonable 65 degree day, and the smell of fuel was very strong. So yeah, fuel might be boiling in your tank on a warm enough day. It's just not rolling and bubbling like a teakettle on the stove. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~