how can i fix these rust spots?

[bama350z 10+ year member]

Por-15 or rust bullet

 

[chrisdwnng 10+ year member]

Sorry to be the bearer of bad news, but more than likely do to a design flaw, that rust spot below the gas door is from the back side. Its the same way on my 1998 oldsmobile.

Water and dirt gets kicked up by the tire into a space in between the fender and an inner structure. And it rusts from the backside all the way through.