Which spark plugs are the best to fit? I've read that NGK are the preferred brand but I'm unsure if they are iridium or standard, I assumed standard but it's a while since I fitted plugs to a Fiat. Our new 500 is three years old but is quite lumpy, not a misfire just not smooth. It's had 3 services but no record of a plug change. I'm guessing the only reason to go iridium is that they last longer?

Yes iridium plugs are meant to last longer.
How many miles have your plugs been used for?

In my experience - NGK only.
You didn't mention what engine version you have?
Platinum or Iridium are standard for the TwinAir depending on the model. I would purchase the standard recommended NGKs for the 1.2, as other than longer life, you get no other performance advantage on the 1.2.
The last set of NGK lasted 18000miles and three years on our 1.2, happily with no loss of performance.
Then the Abarth mechanic changed them for Bosch plugs which promptly failed at 50miles and 1300miles (yes two crap sets)!

It's a 1.2 500s. We have no idea if they have ever been changed so we will get some NGK's tomorrow. My husband knew the twinair was iridium as he worked on Fiats when the twinair was launched. We weren't sure if they had changed on the 1.2 at a later date as well.
Thanks for the replys

Tattyish said:

It's a 1.2 500s. We have no idea if they have ever been changed so we will get some NGK's tomorrow. My husband knew the twinair was iridium as he worked on Fiats when the twinair was launched. We weren't sure if they had changed on the 1.2 at a later date as well.
Thanks for the replys

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I fitted Denso Iridium to our 1.2 can be got for about £26 delivered on Ebay a set.
http://www.ebay.co.uk/itm/4x-Denso-I...kAAOSwB09YQZbJ

Note these are for the 2009 1.2, "seem" to be the same for later cars.

Thanks for the link. My husband will see what he can source tomorrow to see if we can cure the roughness

My husband has fitted some NGK ZKR7A-10's after work this evening. A quick run round the block and it still feels a bit lumpy but we will know after a better run tomorrow. He seems to remember when he worked with Fiat some 500's did this and others didn't but he can't remember the reason. On the plus side the plugs looked original so it was worth changing them

Tattyish said:

My husband has fitted some NGK ZKR7A-10's after work this evening. A quick run round the block and it still feels a bit lumpy but we will know after a better run tomorrow. He seems to remember when he worked with Fiat some 500's did this and others didn't but he can't remember the reason. On the plus side the plugs looked original so it was worth changing them

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The above will work fine but are not(as far as I can tell) Iridium so will last only two years at most(5 for Iridium), try some Super Unleaded from say Shell when the tank is pretty much empty fill it with that may or may not make any difference, also check the plug leads and air filter, after that it requires some more technical investigation.

We have no issue with changing every 2 years. The air filter was changed last October according to paperwork that came with the car. Good idea about the fuel as when we got it we just used the local super market. I will try that at the next fill up, probably Saturday or Sunday. It's a strange feeling, you almost feel it in your stomach rather than a running issue? My husband is getting frustrated as he's seen it before a few years ago. He's now wondering if it's different wheels giving a different drive

I put 1 in every 5 of super unleaded in mine and it may just be me, but it seems to run better for that tankful
0-9 twinair with turbo !