I changed ont O2 cause I broke it, the truck just turned 40K earlier this week, Im not spending $500 every couple of years changing O2's. The 20-22MPG down to 15 was due to using low octane gas with a high octane tune. Under 80-85 it wasnt that big of a difference. I dont worry much about mileage, but I do watch it. Of all the vehicles Ive owned which has been a lot, every one of them has always gone from full to empty every tank, so......gotta have gas.
I agree about the plugs, 100k mile plugs or no, Im gonna change them before that. That being said, I usually replace with the NGK TR55's, NOT the TR55i(x)? I dont usually replace with irridium. I feel more comfortable changing them ever 20K miles with $20 worth of plugs as opposed to $65 every 100k miles

 

Wow! Only 40k on a 2000 model, that's awesome. No, I'm not sayin spend $500 on o2's every couple yrs. That put a person in the poor house just doin o2's alone. For some reason I thought u had over 100k. Gotcha on the octane tune. If changin o2's often I'd change that fronts if I had to pick instead of all 4 if on a budget. I was sayin 100k on stock platinum or iridium, whatever '02 Silvy came stock just won't cut it.

You do know that $20 every 20k is more for plugs than iridiums @ 100k. 35% more.
Long as it works for you, & like u said, that makes u more comfortable, just thought I point out.

 

Doh! My bad. I was talking about my 08. My 00 had more than 100k, but I changed the engine pretty regularly
I know the iridiums at $8ea changed every 100k is cheaper than the non Iridiums at $2.50 changed every 20k but in a modded engine, personally I believe more maitenance is required. If nothing else, it gets me under the hood where I may notice an issue that would otherwise go un noticed
besides that, I do agree that while GM says the plugs are good for 100k, it's hard for me to believe they don't have more spark degridation over 100k than the non iridiums have at 20k, hell I could very well be wrong. On my 08, th plugs will be pulled at 100k and replaced with iridiums, on my toy, it'll get the standard non iridiums and changed every 20k or so

 

on my toy, it'll get the standard non iridiums and changed every 20k or so[/QUOTE]