The replacement gas caps which I have purchased in recent years allows pressure to build up in the tank. I do not like that idea. It would seem to lend itself to cause fume leakage into the cab at the sending unit gasket or the hoses on the filler neck.
I assume the design is supposed to be environmentally kind. And maybe it would be for everyone who is not inside the cab...
I drill a 1/8th inch hole in the plastic on the underside of the cap. No more pressure build up, yet no fuel spilling out either. I avoid filling the tank up 100% also.
