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[LFF64]

Any suggestions as to the best type of spark plugs to use the car has done almost 128000 they were last changed at 95000 I think before I had the car . I take it they are on TC  

[LFF64]

I just noticed I am senior member now  

[Elite Pete]

Congrats on the posting

Vauxhall own plugs are the ones to go for

[v6coop]

Have a look here http://www.omegaowners.com/forum/YaBB.pl?num=1164279437 down the bottom lists the part numbers and options. I have actually put the four electrode plug into my 2.5 V6 as I was told it will give a better performance for longer and hardly any more expensive. At trade club prices £14.04 + VAT for 6.

[Andyb]

depends on engine number m8
they are on tc
either
£1.98
£2.56

[LFF64]

I bet  I know which mine are then  

[Tony H]

Have a look here http://www.omegaowners.com/forum/YaBB.pl?num=1164279437 down the bottom lists the part numbers and options. I have actually put the four electrode plug into my 2.5 V6 as I was told it will give a better performance for longer and hardly any more expensive. At trade club prices £14.04 + VAT for 6.

It's generally thought that the twin electrode plugs are best. Some peoples thoughts are that quad electrode can shroud the spark

[v6coop]

Thanks Tony. I suspect this is one of those subjects that has as many opinions as there are members, but is there any independent scientific evaluation of the different designs? I could understand why the aftermarket boys would want a novel design as a USP for their advertising, but why would a manufacturer like GM bother to fit them if they are not as good as the two electrode version?

[Entwood]

I believe the reason for the development of the 4 prong plug is purely down to reducing the service interval.

An HT charge will only jump in one direction at any time, thus causing 1 spark. It will take the path of least resistance, which is usually to the nearest point. Every time the spark "lands" a tiny amount of erosion occurs, which is why old single point plugs had to be "regapped" at quite frequent intervals, and the tip wore away eventually.

Multi-tip plugs wear much less and require no re-gapping as the spark will work its way around the prongs as they get worn away.

Car manufactures go to great lengths to reduce service intervals as this enables them to sell to the fleet markets, hence the fitting of longer life plugs, especially in cars - like the V6 omega - where changing the plugs is a nightmare anyway !!

[v6coop]

That makes a deal of sense to me as to why Vx would fit them, thanks. Would they sacrifice the performance of the plug in order to gain longevity though?

[Entwood]

I doubt the "modern" set up of coil per plug, or DIS on slightly older cars,  loses any performance on 4 versus 2 prongs, the HT voltage is so high on these that the spark will be good and "fat" anyway.

I was advised to get quality 4 electrode plugs (NGK) before the LPG conversion, and LPG is actually harder to ignite than petrol - it will soon find any weakness in the HT side.

[markey mark]

vauxhall only for me had a bad experence with ngk's  

[feeutfo]

bosch make plugs for GM and are cheaper than bosch at
 halfords at  least. Is it 40k interval?
Changed 2 electrode plugs for 4 on my old 2.5 and
 noticed a marked improvement, filling in mid range
between 2 and 4k rpm ish. Old plugs could have been
breaked of course.

[sev]

it wasn't due to service intervals, but probably more to do with emmission controls, the greater number of electrodes, give the spark a better chance of an even flamefront.

It's the thinking behind the twinspark heads on alfa's and also surface discharge plugs.