Hey there buddy sorry for responding so late to your post. Regard which gas I use I use regular (87) octane because my previous car a 2001 Lincoln Continental used premium (91) octane. That was one of the major factors in me getting my new 2011 MKS because I live and work in Washington, DC and gas prices here are high as Hell ($4+) and we have a very poor subway system it is designed to get people into the District but not take them out of the District where everything is at in the DMV (DC, Maryland, and Virginia).