It takes 4.2 quarts and best way and time to measure oil level is having the car on flat level surface with cold engine (leave it overnight) for all the oil to drip down to the oil pan.
4 quarts
4 quarts
4 quarts
4 quarts
4 quarts
4.2
3.9 but 4 will work just fine
3Q but pick up 4Q
About 4.5 quarts
If you mean how many quarts of oil it's 4 if you're also changing the filter. Less if you're not changing the filter.
4.5 Quarts with oil/filter change.
From the 2006 Scion xB owners manual (pg 229): Recommended oil viscosity: 5W-30 Oil Capacity: w filter 3.7 Liters / 3.9 quarts / 3.3imp quarts w/o filter 3.4 Liters / 3.6quarts / 3.0 imp. quarts