Has anyone studied the rate of evaporation of what we call gasoline today? The other night I took the top off a carb to adjust the floats. Left it overnight to finish the next day. More than half the fuel was gone. A few months ago I put 3 gallons of gas in a project car's dead-empty and recently cleaned gas tank. The car has been started about a dozen times and run around the block about a half dozen times, a total of less than 4-5 miles driving. Last night it ran out of gas on a test run. The car has a vented cap and I'm thinking that quite a bit may have evaporated away. Another question is how do I vent a tank in such a way to slow/stop evaporation of fuel?