It should say on the engine oil cap on top of the engine, I believe it's 5w30
Depends on the year. Listed in your owners manual and possibly on the oil fill cap.
The 2012 Toyota Avalon has double overhead cam (DOHC).
The 2007 Toyota Avalon has double overhead cam (DOHC).
The 2005 Toyota Avalon has double overhead cam (DOHC).
The 2003 Toyota Avalon has double overhead cam (DOHC).
The 2013 Toyota Avalon has double overhead cam (DOHC).
The 2008 Toyota Avalon has double overhead cam (DOHC).
The 2001 Toyota Avalon has double overhead cam (DOHC).
The 2011 Toyota Avalon has double overhead cam (DOHC).
The 2004 Toyota Avalon has double overhead cam (DOHC).
The 2014 Toyota Avalon has double overhead cam (DOHC).
The 2009 Toyota Avalon has double overhead cam (DOHC).