Spark Plug Question

[benchan]

Hello,

I'm servicing my 55 reg Aygo myself and was wondering whether I should or shouldn't replace the spark plugs.

I know that according to the service schedule, the plugs should be replaced every 40k miles.

The current ones I have are the Denso Iridium ones which I installed my self five years ago - I have done 30K miles since.

I don't hear the engine misfiring, haven't noticed (any significant) drop in power, and the car does around 120 miles before the fuel indicator drops by one bar from a full tank (the car has a MMT).

Considering that Iridium plugs suppose to have longer life than standard/oem ones, should I be replacing them soon?

Cheers.

Ben

[Ethanedwards]

I doubt they need changing. Why not pull one and have a look at it.

[rajivrattna]

The ordinary denso last a 60000 km . I would not change it to Iridium since you would not see performance increase with them in this car. Just keep it simple and cheap and change only when necessary .

[benchan]

Thanks guys.

Howard, I will pull them out and have a look.

Rajiv, I currently have the Iridium plugs and contrary to what people say about high performance plugs in a small car like the Aygo, I have noticed about 3% improvement in fuel economy (measured over 5 years / 30000 miles) although this may be more due to the fact I've changed to a set of hard wearing (less grip) tyres at around the same time....