A friend of mine helped me with replacing original spark plugs (twin electrode) in my 1998 sienna with "APP3923 Autolite Double Platinum" which I got from PepBoys and is a single electrode.
It wasn't exactly easy and as we where replacing the fifth plug I looked up under the hood and there a sticker saying "Do not use single electrode spark plugs" in five different languages! At this point we simply ignored the sign and put the single electrodes on.
Does any one knows if I have to use "twin electrode" spark plug in sienna 1998 considering that every website I have checked have both single and twin electrodes listed under sienna 98 spark plugs.
If the sticker's there, I wouldn't ignore it. Perhaps Ray can shed more light as to WHY you need dual platinum plugs; my guess would be emissions/economy/carbon build-up. But I wouldn't vary from spec, and when it comes to Toyota, I try to use the EXACT same plug (Usually NipponDenso) because using others has bit me. The only success I had w/Aftermarket was Bosch DP's in the Tercel
The ND or NGK dual platinums can be had at any good parts store such as CarQuest, AutoZone or Advance.
And the reason they list single and dual electrode plugs for your car is, they fit and have the same heat range. Don't use singles...
I have no idea why you need dual electrode plugs. I have had much better luck following the manufacturer's recommendations than ignoring them, so I try to follow them whenever possible.
I've read up on the advantages of dual electrode plugs, but the sticker about not using single electrode plugs wasn't on any models they sold while I was still there. As far as the reason why not to use single-electrode plugs, my guesses would be the same as yours.
I was thinking about this while posting my origianl response. I have the GTS version Corolla, and it required Platinum tipped plugs, with a warning on the hood telling you to ONLY used platinum tips. The Tercel required dual platinum tips, and the '88 Supra (basically the same Yamaha engine as in the Corolla with two more cylinders) also requires Platinum tips.
I also had, before the GTS, an '80 Corolla SR-5, regular NGK's, and after I bought the GTS I bought a SOHC Corolla 4DR, regular NGK's. Seems to be a thing with the Twin-Cams.
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DIS is just Toyota's version of a waste spark ignition system. While it is true that the plugs fire twice as often, one of the firings is during the exhaust stroke and has zero (nada, no) effect on engine performance. That piece of BS makes it sound like some sort of advantage. Typical Toyota marketing BS for what is an inferior ignition system (at least compared to coil on plug). Oh what a feeling! And sheepeople wonder why I get upset with Toyota. I suppose if you are going to baffle people with BS, you might as well be experts at it.
I suppose the dual electrode plugs are an attempt to keep the overall wear rate for the waste spark ignition the same as for a traditional distributor type system or a more modern coil on plug system (those systems only fire the plug once per cycle which is once every other engine revolution). Over a long period of time the wear will be distributed over the two electrodes although only one fires each time the plug is energized (although it is energized twice as often with "DIS'"). Personally, I've had platinum plugs last for over 100K with little noticeable wear, so I see no point in going to dual electrodes. However, for a waste spark ignition it is important that if you use platinum plugs that you use dual platinum plugs. When the spark jumps from one electrode to the other, it erodes the surface. The platinum is not eroded (or is eroded more slowly). In a traditional systems or coil on plug systems, the spark jumps from the center electrode to the outer electrode. In a DIS system, for half of the plugs, the spark also jumps from the center electrode to the outer electrode, but for the over half the spark jumps in the other direction (outer electrode to center electrode). In theory you could install single platinum plugs where for one situation the platinum was on the center electrode, and for the other situation the platinum was on the outer electrode. Manufacturers actually do this for factory builds, but it is too complicated for the aftermarket, so you need dual platinum plugs where but electrodes are protected with platinum.
I'm using Toyota (Denso SK20RII) iridium plugs on my 1998 Sienna XLE. The Toyota part number is 90919-01210 and these are the long-life (good for 100k miles) plugs with 0.70 mm single electrode tip. I think I paid $13.49/each from brandsport.com.
The commonly found Denso iridium plug IK20 on ebay are the 0.40 mm electrode tip. Denso?s recommendation is to replace them at 30K miles.
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