Any auto parts store has it. I bought my last bottle from Pep Boys. The most common brand is Permatex (and I think they make it for private brand labels too). It can be found stocked with gasket sealer and the like. You can get a small tube for about two or three dollars that will probably last a long time for most home mechanics. You can also get an 8 oz bottle for about six or eight dollars with a brush attached to the cap that may keep things a bit neater.
I also use it on spark plug threads when installing spark plugs in aluminum heads. If you find that your alloy wheels sometimes tend to stick to the brake drum or rotor making them hard to remove, a gentle amount between the wheel and the hub flange also helps. I also use it on the wheel studs. One gentle application will last for many, many tire rotations.
According to the label, it is good for -68F to 1600F, or -55C to 870C.
Other uses posted on the label include:
Brake lube assembly and anchor pins (I don't use it for this, I prefer disc brake lube),
Engine head bolts,
Oxygen sensor threads,
Exhaust manifold studs,
EGR fittings,
Starter and alternator bolts.
Look it up on the Permatex web site if you wish additional info.
