I use Amsoil and do 15k OCI on my 2005 LLY. If your interested in using Amsoil send me an email dirtbikindad@aol.com I can help you with the synthetics and extended change intervals.
[CENTER]2005 Silverado 4X4 CC LB LLY [/CENTER]
[CENTER]Air Lift Bags, [COLOR=black]Amsoil F2B[/COLOR], KB IOH Kit, BD Manifold, Fumoto Valve, PCV Reroute, Resonator Plugged, Mag-Hytec Diff Cover & Trans Pan, PPE X STD, 4" SS Magnaflow Kitty Ran Off[/CENTER]
[CENTER][URL="http://www.duramaxfilters.com"]www.duramaxfilters.com[/URL][/CENTER]