Your owners manual should instruct you on how to do this.
The 2008 Toyota Tundra has a 5-speed automatic.
The 2007 Toyota Tundra has a 5-speed automatic.
The 2009 Toyota Tundra has a 5-speed automatic.
The 2011 Toyota Tundra has a 5-speed shiftable automatic.
The 2014 Toyota Tundra has a 5-speed shiftable automatic.
The 2013 Toyota Tundra has a 5-speed shiftable automatic.
The 2010 Toyota Tundra has a 5-speed shiftable automatic.
The 2012 Toyota Tundra has a 5-speed shiftable automatic.
The SR5 is the Standard. You are thinking of the Limited, it the upgraded tundra. (More Chrome and trinkets.)
The sr5 is just the model, there are different models, like base, limited, xsp, xsp-x, texas edition, etc.
In my 2003 Toyota Tundra limited 4x4, I have put up to 22.5 gallons, so it will probably have about a 23-24 gallon capacity.
Toyota Tundra was created in 1999.