Engine oil is the life's blood of your Jeep, and keeping it changed with fresh oil every 3,000 miles is critical to engine longevity.  This write up is a rough guideline for changing the oil and oil filter in a 2003 Jeep Rubicon with the 4.0 inline 6 cylinder engine.  Most of the information will apply to any Jeep, but consult your owners manual for specific recommendations such as which oil to use and how much.

Materials:
6 quarts Valvoline SAE 10w 30 oil
1 Mopar oil filter
1 oil filter wrench
1 ratchet
1 socket, 16mm
1 drain pan

Step 1:
Drive or idle the Jeep long enough to reach the full operating temperature.  This is done to heat the oil enough to thin it which will aid flow.  You want to get as much of the old oil out as is reasonably possible.  Let the Jeep sit parked for about 10 minutes to give the old oil sufficient time to run down the passages and back into the oil pan.

Step 2:
Place the drain pan under the oil pan with sufficient room to catch the oil which will flow out of the oil drain plug hole at an angle.  Using the 16mm socket and ratchet, remove the drain plug.  Be careful here as the drain plug will most likely be hot enough to be uncomfortable (but it shouldn't actually burn you).  To be safe, you can just remove it all the way with the socket.

The angle of the oil draining will decrease as the oil runs out.  Once it starts to trickle, slide the drain pan over to position it to where its still catching the oil coming from the drain hole, but its also sufficiently under the oil filter which is mounted on the passenger side of the engine.

Step 3:
With the drain pan positioned underneath the filter to catch the oil that will drain once you break the filter seal, put the oil filter wrench on the end of your ratchet and unscrew the old oil filter counter clockwise.  I find its easier to access the filter from the top side of the engine, but if you have small arms you may be more comfortable removing it from the bottom.  During this change I accidentally dropped the old filter but it landed in the drain pan which was positioned beneath so I got off lucky in that I didn't have any major spills to clean up afterwards.  When the old filter is removed, use a rag and wipe up everything on the filter mount base on the side of your block.  I tried to get some pictures of the base but couldn't fit the camera without it being to close to focus.  Dab your fingertip with new engine oil and run it around the rubber seal on the new filter.  Screw the new filter into place and snug it up a little by hand.  Using the oil filter wrench and ratchet again, tighten the filter one complete turn after the point of initial contact with the filter base.  Although you could tighten it a lot more it isn't necessary.  A complete turn after contact will provide an adequate seal and tightening it more will be counter-productive in making it extremely difficult to remove at your next oil change.

Step 4:
Since the oil is still draining, take a rag and clean up your drain plug.  Remove any contaminants and old oil from your plug and reinstall it into the threaded drain plug hole.  The oil will probably still be dripping slightly, but you've drained enough by now that any remaining old oil will be insignificant.  Don't over-tighten the drain plug, just snug it up good (consult your service manual if you're concerned about a torque spec).  At this point you should wipe up any oil spills and remove all your materials and tools from under your Jeep since you're done down there.

Step 5:
Remove your oil filler cap.  There will most likely be dirt/contaminants around the oil fill hole so take a rag and carefully wipe all the junk out.  Be careful not to push the dirt into the hole.  Cleaning it up like this will prevent the contaminants from falling into the engine as you're filling it with fresh oil.

Step 6:
Fill the engine with 6 quarts of fresh oil, and wipe up any spilled oil.

Step 7:
I remove the o-ring from my oil cap to clean all the dirt and gunk off it and the cap threads before reinstalling.  This step probably isn't necessary but I'm very particular when it comes to my Jeep.  It takes just a second to do, and makes me feel better knowing I've taken this extra step.  After the cap is clean, reinstall it and tighten until it clicks.

Step 8:
Crank the engine and check for leaks.  The engine will not be primed with any oil at this point so do not rev your engine at least until after the oil pressure gauge shows full pressure.  Look around the oil filter base and the drain plug for any leaks.  Wipe up any spilled oil, and take your old oil to an oil recycling center.  Most all modern auto parts stores will accept used oil, but call around first to make sure.

The process of changing your oil really isn't difficult and can easily be done in less than 20 minutes.  Take your time the first time and after that you'll know everything there is to know about changing your oil.  Its so simple that its a shame I'm required to even include a disclaimer, but in today's litigious society the below disclaimer is necessary to protect me from liability if some idiot does it wrong and wants to blame me.

Disclaimer: Oil should be changed by a professional mechanic, do not attempt this yourself.

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