I am sure most of us have used WD-40 and it works to loosen tight/rusted bolts (sometimes or depending on how hard they are stuck). WD-40 is probably one of the cheapest most common penetrating oils out there. I have come across situations where WD-40 does not do the job, even hours later some bolts just won't come loose and the last thing you want to do is break a bolt and drill it out. I then moved to things like liquid wrench or PB Blaster, Initially it was like wow, why have I been using WD-40 when this stuff was available? It's also a couple more dollars per can. (Moving up the price chart). Generally speaking I haven't had any major issues with products like PB Blaster or liquid wrench. Then we move into something I never heard of until yesterday....... something called "Kroil" Koil is $19-$25 for 1 large spray can. The way the mechanic explained it to me is that on really tough bolts like the bolts on your wheel hub that are rusted permanently to the vehicle over 15+ years; Sometimes they will use a penetrating oil and then have to use a blunt air hammer to vibrate the wheel hub to remove it because it will not come off with a breaker bar and elbow grease. Kroil really does eat away at the rust and get into the threads and sometimes the bolts will loosen so much that they come out on their own. Sounds like magic right? So I got on the computer and googled Kroil and its an interesting read....... some people are like it doesn't do anything different than WD-40, PB Blaster, Liquid Wrench; but then you have the counter examples where people in real Industrial fields swear by it as the product to loosen and remove bolts on heavy equipment, use in industrial applications to remove 2.5 inch or longer bolts that are stuck, etc. Even the guys on some of the classic car forums are chatting about Kroil on their older vettes and there are people that are like, right what ever and others that are like I will never use anything else since they found it. Have any of you heard of this stuff? Is it another "Snake oil? or is this product legit?