I have only built my left fuel tank. I used the gasket and the tank does not appear to have any leaks. I did not see any instructions that say not to use the gasket that comes with the sender. I just looked in the previously un-opened box the right sender is in and the only instruction regarding the gasket warns you to use a new gasket when replacing the sender. Unless someone has a tale of likely doom, I am not going to remove the gasket from my completed tank and probably will use one on the next tank.