Transtar Amber is like water when it goes on so it gets in the seams and pinch welds really well. Then it hardens enough so it doesn't collect dirt like Fluid Film. You can build a pretty thick layer of it if you are doing frame rails and floor pans. I can smell it on a hot day. I use it on new vehicles that haven't gotten dirty yet. If I buy a car that has been exposed to dirt or water, I would be afraid of sealing in the moisture with a wax product like Transtar Amber, so I will use Fluid Film instead.