I almost didn't try this because of the price. I'm so glad I did. While it won't loosen all nuts and bolts, it does a much better job then anything else I have tried.

When I owned a stereo store and had electronic workbenches, my technicians all used this stuff to loosen impossibly 'stuck' things.
Additionally, as a car nut, I have used it on car parts from the 30's to daily things around the house that WD_40 and similar cannot touch.
It is NOT a water displacement solvent (The 'WD' in WD-40) and the stinkiness is unique, and fairly lasting. SO be careful where you use it. Not so great for regular lubrication of most things in your house, as it will stink the place up.
It works SO well in getting me out of nasty situations with impossibly corroded and cranky items, that I almost like the smell.
But your spouse probably will not. Store it outside or in the basement, too.
My older brother was a 50's hot rodder and mentioned it during a phone call, and that he couldn't easily find it anywhere in Ohio at the stores. I immediately bought two different types of KROIL penetrating oil , spray and liquid, and sent to him as a gift. He is very happy to have it on his shop bench again!
Now I need to order some for myself again.
It is hard to find any really good 'deals' on this stuff, and for some reason, most hardware and auto parts stores don't seem to stock it , at least in the SF Bay Area (and NE Ohio).
If you get together with some friends and bulk order it, it might be worth checking the price directly from Kano.

Okay... Just forget any penetrating rust buster stuff you've been swearing by for years! I've been restoring, repairing and customizing old cars and bikes for over 42 years. I've used em all, and loved PB. I bought this stuff (at the suggestion of a friend) to squirt into the cylinders of a 1960 Buick 401 Nailhead 73k mile barn find (see my review of the PT 30"breaker bar for more info) as added protection when turning the engine by hand. I sprayed up the spark plugs 3X with PB Blaster over 3 days whilst doing other stuff on the car. 7 came out with much resistance and threads were dry. The LAST one (you guys know all about that!) wouldn't give it up. Twisted it to almost the breaking point...No budge man! Shot a bit of Kroil on it, twenty minutes later it came out like it was coming out of a new crate engine! And the threads were well oiled! Made a true believer out of me for sure. The best part is this stuff's been around since before WWII! It'll become your absolute favorite. However... Cheap it's not, but it won't break the bank and it's worth twice the price! Enjoy rust buster Vallhalla!

Works suer fast on seized screws and bolts. well worth the money.

Converting from another brand that I'd used for 40 years to this product. Little bit more $$ but works great!