Again a question without enough information provided to answer it. What year, & model Buick? All 4 speed A/T are not the same.
The 2006 Buick LaCrosse has a 4-speed automatic.
The 2001 Buick Regal has a 4-speed automatic.
The 2005 Buick LaCrosse has a 4-speed automatic.
The 2002 Buick Regal has a 4-speed automatic.
The 2007 Buick LaCrosse has a 4-speed automatic.
The 2008 Buick LaCrosse has a 4-speed automatic.
The 2009 Buick LaCrosse has a 4-speed automatic.
The 2014 Buick Regal has a 6-speed automatic.
The 2004 Buick Regal has a 4-speed automatic.
The 2003 Buick Regal has a 4-speed automatic.
Motorcraft MERCON automatic transmission fluid for 5 - speed manual transmission ( YES - ATF ) Motorcraft MERCON V automatic transmission fluid for the automatic transmissions
Motorcraft MERCON - V - automatic transmission fluid in your 5 speed automatic transmission