Capacity is 36 ounces. I highly recommend you use Synthetic oil in this air cooled engine. Change it once each year.
Click the link and find your engine for the exact capacity.
sae-30
40oz
A Briggs & Stratton 6 HP Engine takes a little less than 1 quart of oil. When you get to about 3/4 poured in, Stop and check your oil. It may take a hair more but not a full quart.
Champion CJ-8
Should take a Champion: RC12YC
48 oz
48 ounces or 1.5 quarts.
Go to this link and it outlines all Briggs and Stratton engine types and spares including spark plugs. http://www.manddsmallengine.com/briggs/parts/ Most common plug used in B&S is a RJ19LM
Most Briggs engines that small take 1 pint of oil .
check you tube under removing the govenor on a Briggs and stratton
SAE 30 weight in the summer or SAE 10w30 if you use the engine in cool temperatures.