last time i bought TR6s and TR55s they were $1.50 each.
TR55s went in Lownslo06's truck and TR6s went in Ice Cream Man's Trans am.
TR6s have been in my 6L for 30k? miles. one day ill change them.

 

They are AC Delco 41-985 plugs ("assembled in USA with Japanese and US parts" is inscribed on the base). I bought them at O'Reilly's...11.85 list,6.99 net per plug.

I've heard of the NGK ones you guys mentioned;I should have posted a question before buying,I guess.

 

funny, when i changed my plugs like a month ago they said NGK and ac delco on the plug, i think NGK makes them for AC

 

Look at that great net price I payed...LOL

 

I have 95k on my original plugs... still runs nice and smooth.

 

Changed my girlfriend's plugs in her 147k mile Explorer... the gap on them was so big and corroded that they didn't even register on the 99 cent gap ring. First time they had ever been changed...

 

Next time just take one out and check it before buying some more. Takes out all the guess work.

 

It's pretty tough to tell if an iridium spark plug is worn, the tip is so tiny. The ground will actually show signs of wear before you notice anything with the iridium electrode. I've never looked at one under a magnifying glass though

 

The main reason I changed them is that I'd heard leaving them in until 100k might give problems trying to remove them. My truck is a little over 5 yrs old and has about 48k;it would be really old by 100k with 1000s of heat cycles.

 

I think that's a good call. It costs like $16 and takes an hour or so and it can't hurt anything.

To others changing theirs, make sure you use anti-seize when you're putting new ones in though, makes it easier the next time or when you put LTs on.