spark plugs, GT vs ST Options

[Hanyo]

yet another spark plugs question.


Just did a service on my celica today and took out the spark plugs.

The old spark plugs look great considering they have been in there for around 50k miles.



Seeing the great wear I am getting on those denso plugs; I decided to put the exact same plugs in there. The car starts fine and is silky smooth now.


The problem came up when I did some further research on these plugs; They turned out to be one heat range hotter then the stock OEM spark plugs. Further detective works revealed they where designed for the 5sfe engine.

So here is the question:

Who else runs a hotter spark plugs in their 7afe? My main concern is I fill up with 87 California gasoline which has the worst octane rating compared to the other states and detonation could be a problem.

So should I toss these spark plugs out and put in the right heat range? Or should I set it and forget it considering they ran well for the 50k miles that I put on them?