Loctite 271 High Strength Red Threadlocker

The low viscosity really makes it easy to wick into tight threads, and even after a day in the garage, I couldn’t budge the bolt I put it on. This stuff absolutely locks everything down, just as advertised for permanent fastening.

Used this on a stubborn exhaust manifold bolt that kept vibrating loose, and it hasn't budged since. The low viscosity made it easy to apply even on that tight, vertical spot.

My old bolt on the lawnmower kept backing out but after cleaning it and using this, it hasn't budged at all. The high-strength formula is perfect for a permanent fix and the low viscosity really lets it seep into the threads.