I have been using it about every other oil change since 103,xxx miles and my car has 128,xxx miles on it now. When I first started using it, I noticed an increase in preformance. Not a huge difference, but it did help the car run better. Knock on wood, I have never had a problem with the engine itself so far. I would reccomend it too anyone also, but I try not to use it with every oil change. I am going to be building another engine soon to replace the one I have now, just trying to keep downtime to a minimum(and I can't pass up a $25 price for a 90 6 bolt with roughly 90,000 miles on it

). So once the new motor is built, I am going to tear down the old one and check everything out and see how the wear is on everything. So far I haven't done a compression test, but I am going to try to get around to it this summer, just to see how its holding up.
Josh