If engine parts are insufficiently lubricated, or a low-quality lubricant is used, with heat and pressure they may sieze (or stick together, as if welded).

I've noticed a few people are into anti sieze products. I have been using just molybdenum grease (not molybond) as an anti sieze compound, since it's ...
www.vectorbd.com/peugeot/archive/97_10/0116.html

Loctite anti-sieze compounds area a group of premium quality products, developed to protect metal parts from rust, corrosion, galling, and siezing. ...
gsgindustrial.com/searchresult.aspx?CategoryID=29

Lube the splines of the clutch disk with high temp antisieze. Also put some antisieze grease on the inside of the hub of the throw out bearing
http://members.cox.net/cglabe1/SM420/sm420.html


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Note added at 1 hr (2007-03-22 16:07:10 GMT)
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In light of what is said in the Loctite site Kim refers to:

La Gamme de pâtes Anti-Seize Loctite® constituée de produits de haute qualité, a été spécialement dévelopée pour proteger les pièces métalliques de la corrosion, du grippage et de la soudure.

maybe "anti-galling" would be more appropriate (if less common?)

galling. A condition whereby excessive friction between high spots results in localized welding with subsequent spalling ...
www.calfinewire.com/glossary.htm

galling
(1) a condition whereby excessive friction between mating parts results in localized welding; subsequent spalling and a further roughening of the rubbing surfaces may follow; (2) a severe form of scuffing associated with gross damage to the surfaces or failure.
http://www.justinline.com/glossary/glossary.asp?letter=G

Stainless Steel and Anti-Galling Lubricants. thread367-76518 ...
www.eng-tips.com/viewthread.cfm?qid=76518&page=10

Fel-Pro Heavy Duty Anti-Seize is a high-temperature, anti-galling. lubricant designed for screw threads and other mated components. of all types. ...
manufacturing-fabrication.globalspec.com/Industrial-Directory/Anti-galling_Applicator

To solve this problem, one plant switched to using Molykote, a lubricant from Dow ... Anti-galling properties can enhance chip evacuation in machine tools, ...
www.motionsystemdesign.com/Issue/Article/24528/Sugarcoating...