I was checking the gaps on my spark plugs with one of those spark plug gap tools from autozone. I saw this special gapping pliers in performance products magazine that seems to be more accurate in getting the gap you want but costs 40 bucks. Should the gapping tool at autozone be sufficient or should one invest in one of these gapping pliers?

What type of plugs are you buying? I believe Bosch plugs are pre-gapped. If you are using one of those gapping disks, then I can see why you would want something more accurate. In the past I used the type that has different thickness wire hooks to it. It sort of looks like a "Chinese star". It really doesn't take much to bend the ground electrode on a sparkplug to adjust the gap. Again though, I think Bosch plugs are pregapped. NGKs are another brand that come pregapped. I am sure there are others, but can't think of them right now.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
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Yea it is one of those gapping disks for under a buck. Im using bosch super copper plugs they are gapped at 32. I read on all the past posts that the gap should be widened to 34 to 40 for better idle. I am experiencing a little roughness in idle quality. Are there any better gapping tools out there that are more accurate that can be found at local auto parts stores? Larry bible recomended opening the gap to 34 for the 300e others recomended opening up to 40.

do you happen to know what the gap is for a 190e 2.6 that will give it better idling? I use the wire type spark plug gapper and it works well, and yes the electrode is very easy to bend. Ken

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Ken
87 190E2.6

Guys,
The general consensus is you should always check spark plug gaps when installing new plugs. The time to do this is minimal and should be automatically done. I have been surprised more than a few times at the inconsistencies discovered, regardless of the manufacturer.

For this you can use any type gauge on new plugs, but only a wire gauge on used ones because the ground electrode wears unevenly through use.

For new plugs I prefer a round gauge with a tapered ramp so you can quickly insert it and rotate to get your reading.