Nathan Munns - Spark plugs. Non resistor, Resistor. Conventional, Gold palladium, Platinum, Iridium

The differences in spark quality with a basic conventional single electrode non-resistor and resistor plug. Gold Palladium and platinum fine wire types, And also the very latest Iridium TT (Twin Tip) by Denso.

As you would expect, with a conventional plug, non-resistor produces a stronger spark.

However, The fine tip of the iridium delivers a much more concentrated and intense purple colour. Especially the twin tip appears superior to all the others even though it has a resistor.

But these differences between any of the spark plugs would still be hard to detect in terms of increased engine performance. If your plugs and ignition system are in good condition you should be fine using any plug. But you may gain a more stable idle, faster engine starting and possibly a couple of horsepower with the Iridiums. Just don't expect miracles.