i heard that you can't use syntthetics after you engine is over 100,000 because it may get leaks or something

 

Are you sure about the coating...I've heard the same thing and then heard it was a hoax. Somewhere there was a test of running a motor dry with the synthetic vs. conventional and there was no significant difference. There is no question that the lubricity is better but it is in the eye of the beholder whether or not it is worth the increased cost.