What's the 2002 Infiniti QX4 engine oil type?

You should only use oil that has the API certification mark on the front of the container. If that is unavailable You can use an oil with an API grade SG/SH, Energy Conserving I & II or API grade SJ, Energy Conserving oil. The recommended viscosity grade that You should use is SAE 5W-30, using any other viscosity could seriously damage the engine. Synthetic oil is preferred although a conventional oil can be used as long as it meets the same standards and has the same viscosity rating. You should manually inspect the oil level as often as You can, every time You put gas in the tank is a good habit to get into. Pull the dipstick from the tube and wipe it off using a clean cloth. Put the dipstick back into the tube making sure it goes all the way down then pull it back out. Hold the tip down and look near the tip and verify the oil level, if it is below the min mark and enough to bring it back within range.