type of grease to use on Aluminium

["sujit roy" <sujitroy@hotmail.com>]

I've seen people use a special type of grease that they use on spark plugs 
when installing them into aluminium cylinder heads.  This grease, I'm 
assuming prevents dissimilar metals causing a reaction.  Is there a 
particular brand that I should use here in the states?  Is it also a good 
idea to use it on bolts that go into the cylinder head?
I'm also assuming this grease can with stand extreme temperatures.

Sujit
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