This is something every warranty-holder needs to understand.

http://www.ftc.gov/bcp/conline/pubs/buspubs/warranty.htm

That's simple reading concerning the Magnuson/Moss Act...google for more wordy stuff.

Thanks for posting the information! 

*** I like this part:

"Tie-In Sales" Provisions
Generally, tie-in sales provisions are not allowed. Such a provision would require a purchaser of the warranted product to buy an item or service from a particular company to use with the warranted product in order to be eligible to receive a remedy under the warranty. The following are examples of prohibited tie-in sales provisions.

In order to keep your new Plenum Brand Vacuum Cleaner warranty in effect, you must use genuine Plenum Brand Filter Bags. Failure to have scheduled maintenance performed, at your expense, by the Great American Maintenance Company, Inc., voids this warranty.***

If a manufacturer requires that you use their parts to keep a warranty valid - they must provide them free of charge.

Yeah, I learned that one a while ago.

Tricky bastards. hahahahaha we win though.