When you switch to Evans coolant you need to change your coolant filter about every week to start with. The coolant will totally clean your entire coolant system and the filter is constantly filtering debris. I would recommend running one week, change your coolant filter. Cut the old filter so you can actually see and inspect the filter element. You will see the gunk and grime on it. Repeat this process every week until you see that your filters are coming off absolutely spotless. After that your good to go. I would expect that the older the engine, the more gunk, grime, and debris that will be in it. If you don't do it this way your filter will clog and your coolant becomes contaminated, which is why you hear people saying it worked great for a while then thickened up and ran hot. Once the entire cooling system is cleaned, pitting and cavitation shouldn't ever be a problem, and it should be a life time coolant that can withstand the higher temperatures.