Spark Plugs

I just bought a 2001 grand prix gt with 135,000 miles. I can`t find any indication of the plugs being changed. What brand/type of plugs have users had the best performance from? What is the correct gap? Are there any tips from users when changing plugs to complete the job with ease?

Welcome to AF.

Your post has been moved from Tips & Maintenance to the regular part of the Grand Prix forum.

stick with OEM AC-Delco Iridiums, part# 41-101. NGK (ITR4A15) and Autolite (APP606) both make quality replacements if you can't find the Delco in your area. I would advise you to avoid Bosch (especially their multi-electrode +2 and +4's) like the plague. Most platinum/Iridium plugs shouldn't be re-gapped, as you can knock the platinum/iridium disc off and cause more harm than good.

I wish I could say i knew , but I don`t so I`ll ask, is there a quality/performance trade-off between the autolite APP606 and a AP606? The AC-DELCO plugs cost more but are the autolites a big drop off?

The AL APP is double platinum and last longer since the AP are single platinum. Basically the APPs are a 100K mile spark plug just like the AC Delco Double Platinum or Iridium. IMO just as good as AC Delco and NGK.

Plus ALs are cheaper because you can get them at Walmart.

As bnaylor stated, the difference is single platinum (only on center electrode) vs double platinum (both ground and center electrode). Since GM's DIS use a waste-spark system (the plugs fire on both the power and the exhaust strokes), single platinum plugs don't last much longer on these engines than non-platinum due to wear on the ground electrode. IMO, if you're looking to save money, buy regular 606's. For longevity, go with the APP606's.

Yeah Rich, I don't recall telling anyone but I switched out to AL APP605 in my Regal GS back at around 45K miles. It has not missed a beat and fuel economy is good. Although there are no mods on it I run one range colder so I can use mid-grade gas. Hard to say what the gas prices will be this summer most likely high but I can minimize any possible KR. However, I keep the AC Delco 41-101 Iridiums as back ups just in case.

I'm still looking for anyone that wants some crappy Bosch Platinums for free. You can't even give them away. :lol:

Bob, I thought we promised to stop beating up Bosch plugs, :lol:

Thanks guys. I found out today new plugs at 91,000. has 135,000 now. The 100,000 mile ac delco plugs look ok. and runs good so guess i`ll put some miles on it and see how it performs. don`t think i`ll go with botched, er, i mean bosch when i do.