Not quite sure as to what the Nissan engineers were thinking when they designed the 3.3 V6 that goes in the Xterra, Pathfinder, etc... My wife's 02 Xterra has a oil capacity of 3 and a half quarts ...with the filter. The filter , I believe is a Fram Ph7317, which looks like it would be better off filtering the oil from a Briggs and Stratton engine. Since we met I have been doing the oil changes on it (currently at 135k miles), my mouth hit the ground when she said she normally had an oil change every 7k or "whenever I remembered" as she said. But to my suprise to this day the Xterra doesn't leak or burn any oil. Even after 4,000 miles it is still full on the dipstick. Pretty stout engine IMO lol... Ive decided to run Mobil Clean 5000 5w30 and a Tough Gard filter with a OCI of 3,500-4k, but im open to what you guys think with an engine that has such a small oil capacity...