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Over the last couple of years there has been alot of conflicting views in the smart world whether or not they are worth the money over a standard plug; even to the extreme of people claiming they have caused damage to their engine as a result of use.

We thought we'd go over these quickly. Alot of people aren't sure just what they are, what they fit and if they worth the upgrade.

Iridium is an incredibly hard metal so makes good for the construction of spark plug electrodes. A precise laser is used to weld the Iridium tip to the spark plug.

Iridium has an incredibly high melting point (Approx 2450°c) and a very impressive strength (approx 8 times that of platinum).

Below you can see a picture of a standard Denso plug for the smart with the 'U' groove electrodes.

The following is a photo of a Denso Iridium plug, also for a smart.

These sophisticated properties of Iridium enable the centre electrode to be made to a much smaller diameter than that of any other material.

Due to the ultra thin tip, the spark can be focused resulting in less 'spark jump' voltage, putting less strain on the ignition system.

The claimed benefits of these plugs is to provide improved fuel economy, increased power/acceleration, better throttle response and service life. These plugs will cost more than standard (upto three times in some places) with very little gain.

We'd like to state that Iridium plugs are only available for 599cc smarts, Please do not try to fit Iridium plugs to your 698cc car even if suppliers claim they are compatible as they are not!

We have spoken to Denso and NGK (the leaders in this technology) and neither have anything Iridium for the 698cc or 999cc engines.