There are 3 common sizes of oil filter for the 8.1 ..... half quart, one quart, two quart. The half quart is the stock size, sounds like someone put the one quart filter on. As mentioned earlier, just refill with more oil if you use a bigger filter (always check the oil level when done). If you use the search feature of the forum, the different sizes have been discussed (beaten to death) previously. Note ........ I choose the one quart size filter to use. I believe quality supersedes quantity in choosing an oil filter for the big block engine.
George R. - Fulltiming since January '03
2007 Newmar Mountain Aire 3991
2012 Chevy Malibu LT1