My plugs arrived today from Rock Auto. I just ordered them at 1 PM Monday, and they shipped them that same day. It only took me a little over an hour to install them in my 99 STS. I would like to thank Submariner409 for the instructions and moral support. Here's some pics of the old ones. Do they look any better or worse than typical 9 year old plugs with 113K on them? Thanks....

http://pic20.picturetrail.com:80/VOL1188/4526177/18459250/308317790.jpg

http://pic20.picturetrail.com:80/VOL1188/4526177/18459250/308317793.jpg

http://pic20.picturetrail.com:80/VOL1188/4526177/18459250/308317792.jpg

4&6
me no likey.....

I would pull the new ones on 4&6 and see what they look like after 1000 miles or so. They look like the ones I pulled from my infiniti when it was running way too lean.

I forgot to mention on the close-ups that the upper pic has the even numbered plugs on the top and the lower pic has them on the bottom. Isn't #8 as bad or worse than 4 & 6? If not, why?

They look A LOT like mine that I did at 110,000 miles I believe. http://gallery.iametarq.com/cars/cadillac%201998%20seville%20sls/engine/spark%20plugs/

except for my one that was arcing. :)

6 looks like a slight oil control problem.

4, 6, & 8 look lean..

8 also looks like burnt oil and adding fuel system cleaners, mostly deposits from these two factors in the combustion chamber.

1, 3, 5, 7, look normal.

How does the car run now with the new ones ?

Thanks for the replies, everyone. It didn't really run badly before so I didn't really notice much difference when I drove it 1.8 miles this morning. I'm just hoping the mileage will increase from 15 mpg to close to 20....

Actually, for 113,000 miles , none of them look all that bad. Wonder how many sparks have jumped those gaps?

Good lord, probably millions or billions.

Actually, for 113,000 miles , none of them look all that bad. Wonder how many sparks have jumped those gaps?

Hmmmmm....Ok for nice, round, conservative numbers, let's just assume that on average those miles were racked up at 2000rpm at 60mph. That's one mile per minute and 1000 sparks per minute, or 1000 sparks per mile -- or 113,000,000 sparks, per plug. Of course that's a very conservative number, as average rpm is likely to be higher and average speed lower...and this doesn't take into account all the time spent idling. If the average is 3000rpm and 40mph, now its 2,250 sparks per mile, or 254,250,000 sparks.