Carbon build up on spark plugs

I replaced the plugs yesterday at 59,300 miles. I have been tuned (OTT) since about 26k miles. My truck is mainly a daily driver but is set up to be a tow rig when needed. When the plugs were replaced I had noticed carbon build up on the lower 1/8" of the threads on all of the plugs. Cylinder #5 plug had oil on the threads, the rest were bone dry. I am not used to seeing any build up of anything on plugs and am wondering if something is going on. After I replaced the plugs, the MAF sensor was cleaned (wasn't dirty to the eyes) and cleaned the throttle body. Air filter is the K&N oiled; I have never had any issues on my personal vehicles with oiled filters with MAP or MAF sensors with over 100k miles per engine of reliability to go off of. But the filter is clean and no oil film on MAF.

Is there an issue going on here or is this normal being tuned?

 

consult a spark plug guide

looks good to me.

 

Looks good to me too.
I find that I get cleaner plugs when I use Top Tear gas exclusively.

 

I’m curious what octane are you using and is it a top tier fuel?

 

99.9% of the time I fuel up with Sunoco 87oct. My OTT tune is for 87oct. If I'm towing in higher elevations it's 91oct but that's rare. I'm just used to plugs looking dry and rusty in color and not sooted like these. The soot at the exhaust happened quite litterly over night.

Now that I have about 90 miles on the new plugs, fuel economy based off of the trip summary has improved about 2 mpg from 17ish.

 

I have found higher octane fuel burns cleaner but I would say with original plugs and 59,300
your plugs look fine to me.

 

Are you trying to create a problem here?

 

This..

Those plugs look like they still have a lot of life left to give.

 

I'm a bit confused here. 60k mile spark plug life expectancy as well as a required component to be replaced at 60k miles. Platinum iridium last for 100k miles, not ones we install. My fuel economy nearly got a 2 mpg bump. What all started this was my exhaust suddenly going from a dirty bronze in color to a black soot. Soot in the exhaust is something I'm not familiar with and seems like a bigger problem in the long term.

 

Here’s my original plugs from my truck bought new in December of 22. They have well over 100k on them.


Not a thing wrong with your plugs.

 

60k is Toyota recommended service… not sure why so early on spark plugs . I can see this if u tow and off-road a lot . Everyday driving don’t see the point. Of changing that early . Most vehicles I have owned changed at 100k .. plugs u have look good . Maybe u had some plugs that were loose and using cheap gas why u had some dark build up in the exhaust .