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Discussion Starter · #1 ·
bought some rs plugs from pumabuild and they turn out to be exactly the same part no as the st plugs that came out.

so whats the big fuss about getting rs plugs. bit dissapointed really.
 

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QUOTE(denboy @ 18 Nov 2009, 09:14 PM) <{POST_SNAPBACK}>bought some rs plugs from pumabuild and they turn out to be exactly the same part no as the st plugs that came out.

so whats the big fuss about getting rs plugs. bit dissapointed really.

There is a difference, i just can't remember what it is?
 

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The RS and ST get the same plugs fitted in the factory.

But

If you buy ST plugs from a dealer they are different than the original plugs - different part number, actual physical differences unknown.

The only way to get the same plugs that you took out is to buy the RS specced ones.

Simples.
 

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There is another post on here somewhere which states the difference between the two plugs.

From memory there are two sets numbers associated with each set of plugs and one set of numbers are the same while the other is different.

When i purchased a set from my local dealers they even said that ford cannot guarantee they they will work in the ST.
 

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Discussion Starter · #8 ·
QUOTE(troy45 @ 18 Nov 2009, 09:27 PM) <{POST_SNAPBACK}>The RS and ST get the same plugs fitted in the factory.

But

If you buy ST plugs from a dealer they are different than the original plugs - different part number, actual physical differences unknown.

The only way to get the same plugs that you took out is to buy the RS specced ones.

Simples.

last time my plugs were changed was in december 2007,was the rs2 on the road then,if not,that just means they are putting st plugs in rs,s.

if you get my drift.
 

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QUOTE(Johnpro @ 18 Nov 2009, 09:27 PM) <{POST_SNAPBACK}>When i purchased a set from my local dealers they even said that ford cannot guarantee they they will work in the ST.

But they did ... and my car is living proof !!!!

The ones I fitted (RS ones bought from Ford dealer) were a different part number to those I removed.

My car is a 55 plate so an early model so original plugs may be different from what Ford fitted in the later models.

All I can say is the car is running better with the RS Plugs fitted.

P.S RS plugs are cheaper than ST ones too !!!
 

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The Ford system quotes the following part numbers for the Plugs

RS Plugs FINIS 1583231 7G9N 12405 AA
ST Plugs FINIS 1505812 6M5J 12405 AA

Maybe Ford have now updated the ST plugs to RS ones - I will check to find out
 

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Just had a look on Fords system and ST/RS plugs are listed differently, all I remember is the plugs that used to come out of the ST's had "Volvo" on them and they used to come as a set of 5 under finis 1371606 in a Volvo box!

Ford rebranded the plugs Fomoco and they then came in Ford boxes, I haven't seen an RS plug but I can't imagine them being the same as the earlier ST plugs which had "Volvo" written on.

My opinion is Ford wouldn't list two different part numbers if they are the same, must be a technical difference?
 

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QUOTE(NickC @ 19 Nov 2009, 11:42 AM) <{POST_SNAPBACK}>Just had a look on Fords system and ST/RS plugs are listed differently, all I remember is the plugs that used to come out of the ST's had "Volvo" on them and they used to come as a set of 5 under finis 1371606 in a Volvo box!

Ford rebranded the plugs Fomoco and they then came in Ford boxes, I haven't seen an RS plug but I can't imagine them being the same as the earlier ST plugs which had "Volvo" written on.

My opinion is Ford wouldn't list two different part numbers if they are the same, must be a technical difference?

this is correct , when my 06 had new plugs the original ones had 'volvo' on them.
 

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my car is late 06 and the plugs that it had from factory are exactly the same as the RS plugs that are in now. Part numbers are different all the labels on the plugs themselves are identical.

Haven't had any problems with stock plugs, changed to denso (idiot, got misfire), went back to stock (RS) - smooth as baby's bum.
 

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Right - I have been looking into this further. - I am becoming a spark plug geek

We need to be looking at the last three small digits stamped onto the main body.

2005-2006 ST spec Plugs (marked up as Volvo) - 8658474 789

2006-2007 ST spec Plugs (Marked up as Fomoco 7G9N12405AA) - FR7N133 - 789

2007- ST spec Plugs (Marked up as Fomoco 7G9N12405AA) - FR7N133 - 592 & 687 & 690

2009 - RS Plugs (Marked up as Fomoco 7G9N12405AA) - FR7N133 - 983

It might well be that the latest ST plugs are 983's however we do not have any instock to check

I have now gone through approx 10 sets of old plugs to check the numbers stamped onto the plug body.

We understand that the last three digits refer to the plug temperature
 
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