While I agree that you should run dyno-juice for the first 1,000 miles for a better break-in. Nobody can "void" a warranty based on the use of an oil that meets the specifications. Unless they provide the "correct oil" free of charge. See the quote below.

While the Magnuson-Moss Act does not require manufacturers to provide a written warranty, it provides specific rules when one is provided. Among those provisions, FTC regulations state: ô(c) No warrantor of a consumer product may condition his written or implied warranty of such product on the consumerÆs using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the Commission if û ((1)the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and (2) the Commission finds that such a waiver is in the public interest.ö ((42 U.S.C.2302(C))

That means your warranty stands when you use AMSOIL Synthetic Lubricants.

Vehicle manufacturers recommend lubricants according to their viscosity grade and service classification. Any oil, whether it Æs conventional petroleum motor oil or synthetic, meeting the correct viscosity grade,5W-30 for example, and the current API SL and ILSAC GF-3 North American service classifications may be used without affecting warranty coverage. AMSOIL motor oils are recommended for use in applications requiring these specifications.