Spark plug Bosch or Denso

I finally changed out the OG Denso spark plugs on my wife's '10 RX350 at a shameful 415,000 kms. Wasn't idling rough but some low-rpms hesitation. Plugs still basically worked fine, though.

Your observation is correct.

Bosch is the original manufacturer. Buying from them will be cheaper. Mercedes genuine just means they take the Bosch part and slap their name on it to say "yes, this component is up to our standard".

Toyota sounds like great deal if they actually use OEM plug (DENSO iridium). That part alone is \\~$18 each (you need 6).

DENSO , Iridium Long Life, SK20HPR-L11 Spark Plug

I would stick with the specd Denso, leave the coils alone.

I already replaced the spark plugs with the Denso ones I listed though... Is this bad?

So i just ordered a pack of 4s (the left one is from Denso Japan) from a local distributor carrying Denso spark plugs and of the 4, 3 are made in China and 1 is made in Japan. Comparing them side by side, the China ones definitely look subpar to the naked eye.

definitely not ok, they are spent, also Denso>NgK any day of the week

My s2000 ate the Bosch plugs I put in, which were rated for the car/f20.

The previous owner had installed some Denso IKH24's that looked..... disgusting. In fact, I have NO CLUE how the car ran as well as it did, as the tips from the Denso plugs were gone, and the gap was 0.055. The car still had a slight miss after I did the coils last month which prompted me to replace the plugs.