Hello! I purchased some NGK Iridium IX Spark Plugs BKR5EIX-11 # 5464 from amazon (linked). I removed one of my old plugs AFTER receiving these ones in the mail. And it has Mercedes logo and says NGK R.
Upon searching the forum I see a lot of people talking about heat range, etc.... And I saw one person asked if he could use NGK #4969. And someone replied "bkr6eix11's ".

I am trying to perform a tune-up to increase performance and maintain a happily functioning car. No point putting incorrect spark plugs in... I'd rather the old ones leave them in.

And then I looked in the owners manual and it says "NGK PFR 5-11" (or Bosch, but nah), and that has me confused even more!

I have a 2004 Chrysler Crossfire Limited with 144,xxx miles, and has original spark plugs. (I purchased from a coworker's son and he bought the car at 60k miles, never changed the plugs).