i have about 150K+ but its a babied toyota engine, so i'm fairly confident that it'll hold up, but i have heard of other ppl doing on their 200+ cars and it worked wonders, the stuff really is great....but yeah i heard it could unplug sorta speak some possible problems , but hey at least it'll bring them to my attention to fix, that is if i wanna spend the bucks, but yeah i am really pleased with this stuff