This weekend I went ahead and changed the oil, replaced the spark plugs, and cleaned the MAF in my 2006 4Runner V6. A couple thoughts:
I didn't notice that the oil filter adapter plate drain hole drains to the floor, lol, doh! I should have seen that but wasn’t paying attention to it. I lost 10min cleaning up the garage floor but I know for next time to put a catch can under that drain hole when unscrewing the oil filter.
For the spark plugs, I was suspicious that the previous owner had never changed them. Sure enough, when I removed all six I quickly noticed that three were Denso and three were NGK. After 120K miles, the copper plugs (which have a 30K recommended service life) were pretty beat up and I measured the gap at about 0.065" which is quite a bit larger than the recommended 0.044". Surprisingly the car still ran great. I used the Denso stock replacement plugs for the job. The swap was mostly a breeze.
I can tell a difference in how smoothly the truck idles. However in my opinion, the manufacturer’s 30K spark plug replacement recommendation is probably too conservative. My plan is to replace these plugs after 50-60K in the future given that those plugs still worked well at 120K.
Thanks for all the helpful advice everyone.
Luke