The oil you should use depends on the climate you live in. In more mild climates (such as Southern California) the proper viscosity is either 5W30, or just plain old 30W.
As far as brand is concerned, I prefer Valvoline conventional, or Royal Purple full-synthetic.
The 2002 Nissan Sentra has a 5-speed manual.
The 2002 Nissan Sentra runs on regular unleaded.
synthetic valvoline
The 2009 Nissan Sentra has a 6-speed manual.
The 2012 Nissan Sentra has a 6-speed manual.
The 2014 Nissan Sentra has a 6-speed manual.
The 2003 Nissan Sentra has a 5-speed manual.
The 2006 Nissan Sentra has a 5-speed manual.
The 2004 Nissan Sentra has a 4-speed automatic.
The 2008 Nissan Sentra has a 6-speed manual.
The 2007 Nissan Sentra has a 6-speed manual.
The 2011 Nissan Sentra has a 6-speed manual.