This post is to solicit the opinions of readers regarding the choice of spark plug for their Mazda. Have you installed new plugs in your vehicle? If so, what is the year, model and mileage of your Mazda and what brand and model of plug did you choose? If you chose a plug other than the OEM plug, what was your experience with the plug you chose and would you recommend it to others?

I have a 2003 Protege DX, 2.0 L, Non-Turbo, with 30,000 miles on it. Just replaced the plugs for the first time with Bosch Platinum Ir Fusion. Thus far, they are working very well. The car starts easier and idles more smoothly. Overall performance is excellent. The OEM plugs were NGK.
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1996 Protege ES 1.8L 182,000.Had it from new. I have always used NGK except once. I tried Autolites for a year and was not happy with them. So I went back to the NGK. Also noticed a big difference when I put the NGK wires on.

 

Yeah, NGK makes excellent plugs for sure and I might have noticed the same improvement with new NGKs as I have with the Bosch. I was curious about the radical design of the latest Bosch plugs and how they would work in my engine. I'm also curious about their durability, but won't have much of an idea about that for another 30,000 miles (I hope).

As for wires, the car only has two very short wires and no distributor. There are two coils, each connected directly to one of the four plugs and indirectly, by a short plug wire, to one of the remaining plugs. Each coil fires each plug twice per cycle, once near TDC of the compression stroke and once near TDC of the exhaust stroke. They call it a wasted spark system, as the firing during the exhaust stroke serves no purpose. First car I've had without a distributor. Sure do like not having to replace a cap and rotor or adjust timing.
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The coil packs are a known issue with these cars. Should keep a spare handy because they tend to go with no warning. I think they are about $30 each. I would rather have the cap and rotor. That design is one of the things that Ford brought to Mazda, not one of their better ideas.

 

If one of the coils were to suddenly fail, as you say they are prone to do, how would I know that was the problem? Is there a quick test one can perform with a multimeter? Do you know if driving in extreme heat (over 110°F) makes coil failure more likely?

Also, are aftermarket replacement coils available? I mean, if these coils are notorious for failing as you indicate, wouldn't I be better off with a high quality aftermarket replacement as opposed to an OEM replacement? Of course, I'm assuming that Mazda hasn't corrected the problem and are selling the same lot of coils as was used in the manufacturing process and they may have taken corrective action. I don't think I have ever had a coil fail on any vehicle I've owned, but there's a first time for everything.

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I don't know of any test that can be done without the shop computer. They tend to just stop working right. The car will start to misfire. NIEHOFF makes an aftermarket coil pack. But they are $60. Kinda pricey. The thing with Mazda parts is that there aren't too many aftermarket producers of parts. The problem is the design of the pack itself. They are using much smaller pieces that aren't as stable as the old style distributor.

 

Twice as much is indeed pricey. I will stick with the Mazda coils. I think having an extra is a good idea if they are prone to failure. The nice thing is that the two coils are interchangeable. I will get an extra before taking my next road trip to the desert. If the engine won't run and I suspect a bad coil, I can swap one out and if they doesn't work, I can swap the other.
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You always want to have some extra parts in the trunk if you are out in the desert alot. The same goes if you live up in the mountains. You never know when you will need them.

 

Hey getting back to the spark plugs, does anyone else out there want to share their experiences with various manufacturers and plugs?

Thus far, the Bosch Platinum Ir Fusion are performing very well in my 2003 Protege DX. When I refill with gas, I will take my mileage and post the result and how it compares to what I've gotten historically with this vehicle.
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I checked the mileage for the first tank of gas on the Bosch Ir Fusion plugs. It was 26.36, which is pretty much par for my 2003 Protege DX. I did a mixture of city and freeway miles. I had added a bottle of Techron fuel system cleaner and I know that although using such products periodically is a good idea, I also know that they can lower mileage for the tankful they are added to. I will check the next few tankfuls to see how it goes.[align=left] [/align]