All 3.3 supercharged FI MFI Xterra's require premium gasoline.
--- running on regular or ethanol will probably trigger the Xterra's knock sensor in this engine.
Since replacing the knock sensor (code 324 or related) in the Xterra supercharged engine is extremely expensive (figure $650-$750) depending on year and location...
--- use premium.
The "non aspirated" 3.3 cylinder Xterra can use regular gasoline IMO....
--- personally, I would try to avoid ethanol blends (10%) since the Xterra engines are somewhat sensitive to lower grade fuels.
The 2006 Nissan Xterra has a 6-speed manual.
The 2010 Nissan Xterra has a 6-speed manual.
The 2002 Nissan Xterra has a 5-speed manual.
The 2007 Nissan Xterra has a 6-speed manual.
The 2011 Nissan Xterra has a 5-speed automatic.
The 2004 Nissan Xterra has a 5-speed manual.
The 2013 Nissan Xterra has a 5-speed automatic.
The 2005 Nissan Xterra has a 6-speed manual.
The 2003 Nissan Xterra has a 5-speed manual.
The 2001 Nissan Xterra has a 5-speed manual.
The 2008 Nissan Xterra has a 6-speed manual.
The 2014 Nissan Xterra has a 5-speed automatic.