I have a 2003 Nissan Murano 148K, original plugs. I know they need to be changed, I’ve heard that they can be very difficult to do after so long. How much trouble am I in for?
You won’t know until you try to remove them.
Tester
Remove the coils or wires
Spray penetrant, so that it will run down the threads
Let the car sit overnight, so that the penetrant can do its thing
Attempt to remove the plugs the next day . . . slowly
I did plugs for the first time on a 9 year old truck with 98,000 miles and aluminum heads. No sweat, the plugs came right out of a cold engine, no PB Blaster, nothing. Try it, just don’t use a 2 ft breaker bar. If they don’t come out, warm the engine and hit the plugs with PB Blaster, Liquid Wrench or WD-40. Let it sit overnight and try again in the morning. Should screw right out.
I just did my 2005 Camry with 100 K miles last week and it was easy, nothing stuck, no disasters.
& I’d use a little anti-sieze substance of some kind on the theads of the new plugs.
I would opt for the pro-active application of penetrant the day before. I would also bump them clockwise just a hair before starting to unscrew them counter-clockwise. Good luck…
By 2003, all the long life plugs had an anti-seize plating on the threads so they usually come right out. The important thing is to have a good fitting, six sided spark plug wrench and the proper extensions so you are directly over the plug.
I would also use a long breaker bar for the simple reason that they are easier to control and keep the pivot point directly above the plug. If you end up straining with a short bar or ratchet, you are more likely to get the pivot point off center and muck things up. Just don’t use too much torque, if it takes more than a good nudge to break them loose, then go to the penetrant and let them soak for awhile.
you’d be surprise on how stuck it could be…but also surprised that it comes out easy peasy. too many factors to predict. give it a whirl, and you’ll know which option you need shortly. and report back please
Soak the plugs with PB Blast before attempting.
Modern spark-plugs usually have tapered seat seals…100% effective. No penetrating oil can get past that seal and into the threads. They will either come out or they won’t. Use the proper tools. 1/2 inch drive sometimes works better than 3/8 drive. As a LAST resort, try tightening a stubborn plug just a hair, don’t overdue it, then try to remove it…Once you move it a half turn and break the seal, they should turn out easily and smoothly. If they want to stick and drag, THEN soak them with penetrating oil and work them back and forth until they free up…If a plug suddenly offers resistance while removing it, STOP, give it some oil and screw it back in a turn or two then carefully work it out…
A silent prayer before beginning might not hurt either…
.Once you move it a half turn and break the seal,
You didn’t mean a half turn in did you?
I always make the sign of the cross when the last one comes out…
Just a few weeks ago I was changing plugs on my daughter’s '05 Mustang and was sweating bullets the entire time because 3 of them turned into a real see-sawing match. What should have taken 15-20 minutes tops turned into 3 hours. I cringed while looking at the threads and praying for no aluminum.
The irritating part was that those plugs had been installed my me snug fit only with anti-seize about 35k miles prior.
Were those the plugs that are about a mile long?
If they are, Champion makes “one-piece” plugs that supposedly don’t break
@db4690, the plugs are the normal Autolite plugs 5143 which I believe is the newer revised number that may have replaced the old 764 number.
Just figured since they were copper core with over 30k miles on them it might not be a bad idea to read them and throw in a set of Platinum 5143s after changing the oil and so on.
After all, what could go wrong on a late Saturday afternoon… 
The only positive note on the evening was that the car is still leak free of any substances and a compression test showed 185-190 on all cylinders at going on 190k miles.
Your daughter’s car has the 4.0 V6, I presume?
If the car had the V8, it would have the mile-long plugs, which have a tendency to break off.
These are the V8 plugs, which apparently break quite often
@db4690, you’re going to think I’m absolutely nuts, but for the Triton 3-valve engines with the mile-long plugs that break off, I’ve never broken one in the head. I remove them from a warm (operating temperature) engine using a 3/8 impact.