Some people still dont know about it and their dealers dont even tell them when buying a MS460

The STIHL Ultra Limited Warranty – Double Your Warranty Protection
Double limited warranty protection applies to STIHL gasoline-powered products purchased for personal non-income producing, family and household purposes only. At the time of your equipment purchase, simply purchase a six-pack of STIHL HP Ultra engine oil or six 32 ounce containers of STIHL MotoMix® premixed fuel to qualify for double the limited warranty coverage. STIHL HP Ultra provides the best engine oil for improved engine longevity. Restrictions may apply.
Effective date: January 1, 2012.
http://www.stihlusa.com/lubricants/engine-oil-double-warranty.html