Denso(5339) ITV20 Iridium Power Spark Plug, (Pack of 1)

I bought a used 2012 Mazdaspeed3 and put these in as preventive maintenance at 60k miles in case the old plugs were originals with 60k on them. The old ones didn't look bad at all and probably had less than 30k miles on them even though they were OEM plugs, which I believe are NGKs rebranded as FoMoCo. I can tell no difference in performance or fuel economy since I changed them, which is exactly what I would expect. These were precisely gapped to what they said on the box, but I needed to re-gap to 0.024 - 0.028" which took a bit of muscle. I'll likely buy these again in another 60k miles.

Denson Iridium spark plugs are good quality...

Plugs work as expected...gaps were consistent

Just what I ordered!

I'm not sure you can "love" a spark plug, but these were fine OE replacements in my mazdaspeed3. They came shipped loose in the box, but mine had plastic sleeves to maintain the gaping. I did confirm the gap was correct on all 4 with my feeler gauge before installing.Upon replacement, the car started right up and isn't showing any signs of having issues. This is the first time I'm using a Denso plug, normally I buy NGK, but the price was better on these so I'm glad the quality seems to be there also.

Work good

I disagree with the other review. This is not a good choice for a stock replacement plug for a Mazdaspeed 3 as these come with a .44 gap out of the box and it should be between .26 to .32 preferably .28 to .30Do NOT re-gap an iridium plug! You will almost certainly damage the core and lose some of the potential, despite probably not even realizing it, as they will probably still run. NGK goes so far as to say it would be better to run it at the wrong gap than to re-gap an Iridium. Especially one with a core as thin as these Densos. If you go step colder in Denso (ITV22) then note it DOES have the proper gap for a Speed 3, while NGK's step colders DO NOT.For these stock heat ranges, use the NGK's instead as they have the proper gap. It should be pointed out that NGK IX's and Laser Iridium's are different plugs. Their IX's are their high performance while their Laser Iridiums are their super long life power performance. The stock plugs in a Speed are Laser Iridiums. In fact, they are re-badged NGK Laser Iridium's that say FoMoCo on them. I doubt you see any improvement in performance in the IX's or the Denso's, but one thing you will definitely see is a much shorter life with quicker easier fouling. I fouled 2 IX's out and 1 Denso ITV22 out when trying them all out. I've went back to the Laser Iridium NGK's stock heat range with the proper gap out of the box and everything is aces again.When you start modding, and go with a downpipe and a COBB AP tune, you will need to go step colder. When you do, go with the Denso ITV22 so no re-gapping is required.Stock: NGK Laser Iridium's. Stick with those unless modding.

Replacing the OEM Iridium spark plugs resulted in a smoother acceleration across the entire RPM range. These spark plugs combined with 91 octane gas (recommended is 87) resulted in better engine performance which is important if you own a Ford Fiesta with the 6-speed dual clutch automatic transmission. Transmission performance improved at lower engine RPM and was smoother at mid and high RPM.