Synthetic oil

I have/had been a believer in Synthetic engine oil for decades and am registered to sell Amsoil. I have always used it in my pickup engines and some class 8 trucks and heavy equipment that I ran during Winter months. I had a headgasket go out on my 5500 GMC. This truck had only 60K on it, but always had Amsoil 15-40. The valve train had a lot more wear on it that it should have given its miles and use of synthetic oil. I ceased all further utilization of synthetic in the engines. I still use Amsoil gear lube in all class 8's and pickup diffs and Amsoil for the automatic trannys. That's my story.