Hi, 2003 1500 4wd 5.9 gas Laramie. In the manual, for spark plugs it says R12LC4. When I looked that up I find Champion Copper. Is that the one to go with. I get conflicting answers. People have told me only go with Bosch, only NGK. Then I also see all these different spark plugs, iridium etc. what is the correct spark plug to go with (brand and material eg copper vs iridium)? Thanks for the help.

 

Copper plugs, manufacturer of your choice. Avoid the rare earth plugs, the older engines just don't like 'em.

 

 

NGK iridum are the best! But you have to put 16 so financially, if you are on tight budget go for economy class but automatically change them after 50,000 KM or 30,000 miles.