As I was throwing out the old spark plugs after my tune up I did a month ago, I noticed the plugs that I thought had been in the car the whole time since new were NGKs. Silly question, but doesn't Chevy use ACDelco as their stock plugs? If so, the only reason for this I figured is that while my mechanic was changing the timing belt and other small things, he must have changed the plugs which he said he didn't. Which also makes me think, since he and I are somewhat friends was he trying to be nice ($30 plugs isnt a big deal, he owns the shop and probably got an even better deal(bulk)) or did he try to impress me after the timing belt was done and make it seem like he did a better job than what was actually done (spark plugs making easier starts and clearing up any ignition issues there may have been) HAHA I know I am probably overthinking things, but after looking at the reciept and the only thing on there is timing belt replacement, I cant help but wonder if he charged me secretly for spark plugs and hid it in the total charge. and in that case, since the plugs were only 20K miles old, did I just throw away good NGK plugs???! LOL I guess Ill have to ask him next time I run into him, if he even tells me the truth/remembers.