Why two brands of plugs

I can understand wanting to have 2 suppliers for parts. But I don't get mixing brands of plugs in the same engine. But it seems to have worked.

FWIW I paid my mechanic to change plugs in my 4.0V6 at 100K and 200K. I'm at 239,000 now. It ran fine before and after changing plugs. No difference in fuel mileage or power but I figured 100K was long enough. I have no idea what brand he used.

 

Nothing wrong with using iridiums in the 1 gr, i wouldn't go for platinums though just a waste. Pulled mine at 104k, no idea if/when last owner changed but they were pretty crusty and gap was well out of spec. Cleaned throttle body while I was at it so not sure how much of a difference plugs made but all together was a huge improvement in running and throttle response

 

My 2011 4 cylinder only has 14,000 miles on it, but maintenance manual says to replace plugs at 10 years so I plan to.
However, the manual calls only for

$59 DENSO SK20HR11 ---- IRIDIUM PLATINUM power pack Spark Plugs -- # 3421 ----- 6 PCS NEW

DENSO SK20HR11, 0.043 in (1.1 mm) gap. But also states irridium-tipped. Do NOT adjust the gap when tuning engine. What if gap is not as noted above? Or does this mean don't adjust the gap in the future?

What is irridium tipped anyway?

Also, what happens if I use a regular spark plug, since I drive it very few miles?

 

You'd be surprised how many people pay more on parts just to think they are getting more power lol.

 

Thought about changing plugs myself - used to do that kind of things. But looked under hood for plugs and couldn't even figure out the wiring. Viewed a couple of videos on how to do it and more effort than I want to put into it. Toyota may have had a good reason, but seems overly complicated to me.
Since only has 14,000 miles, may just wait even though 12 years old.

 

Spark plug change intervals should be negligible as you should still pull the iridiums every 30-50 and verify gap. Also the 4.0 05-11 run way better utilizing the coppers as they burn hotter. Iridiums always ran like crap on the single vvti 05-11. It seems the 12-15 dual vvti 1grfe can run the iridiums better than the single vvti 05-11 but I still recommend copper for all 05-15.

 

Throw densos copper plugs in there, supposed to change every 30k but that is kind of ridiculous