There is not a 2.3. It is a 2.8. The oil filter is on the top drivers side about the middle of the engine. There is a "cover" with a hex bolt in the center to remove it. The cts is a very easy oil change.
The 2011 Cadillac CTS has a V6 engine.
The 2003 Cadillac CTS has a V6 engine.
The 2008 Cadillac CTS has a V6 engine.
The 2004 Cadillac CTS has a V6 engine.
The 2005 Cadillac CTS has a V6 engine.
The 2010 Cadillac CTS has a V6 engine.
The 2012 Cadillac CTS has a V6 engine.
The 2009 Cadillac CTS has a V6 engine.
The 2013 Cadillac CTS has a V6 engine.
The 2006 Cadillac CTS has a V6 engine.
The 2007 Cadillac CTS has a V6 engine.