You may as well put your fuel tank into an oven. Last, as the speed of a car increases, the movement of air over the open fuel tank inlet creates a vacuum increasing with speed. Vaporization is also increased. In total, a stationary vehicle will vaporize less gasoline. Our assessment is all the more conservative.
Lets talk about the mechanics of the screw-on type gas cap.
It is designed to seal with compression related to radial torque on the threaded neck. Newtonmeters, and you have the equivalent of NO gas cap. It is an important statement because you literally can close a gas cap until it physically stops and effectively have no gas cap in place. Newtonmeters, we reduce the vaporization to zero grams HC at .7 Newtonmeters. It is supposed to compensate for wear and tear plus a change in the properties of plastics at varying temperatures.