Oil started coming out from my valve cover and half moons, when I started using 5w-30 oils. My suking mekaniko said I should buy a new valve cover gasket and half moons. Since I live in the province, I could not get orig mitsu parts here. What he did was put silicon on the valve cover gasket and hal moons. and so far there has been no leaks.

My question is what's the disadvantage of using hi-temp silicon vs new gaskets? should I replace it asap even if itt does'nt leak anymore?