Cannot provide a link but this is from the 01/05 GM Service Line;
quote:
The following 2005 engines have synthetic engine oil installed at the engine plant(fig. 7).
2.0L LSJ
3.6L LY7 Cadillac only
4.6L LH2
6.0L LS2
TIP: When servicing these engines, use oil that meets the GM4718M specification, as outlined in the Owners’ Manual. Not all synthetic oils will meet this GM standard.