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[Doctor Gollum]

If they're too long you run the risk of being struck by the piston, and too short and they become shielded by the head and the mixture won't burn cleanly.

Like you said, even genuine plugs are less than a tenner, so really not worth the risk

[Nick W]

Ditching distributors and points based ignition arrangements for high ouput mapped systems is the root of longer plug life. FI further improved it.


100k intervals don't appeal to me though.

[Enceladus]

I've put Omega plugs in all sorts of cars without issue  if they fit they've always worked

Interesting. I was taught that plugs with too hot a heat rating would oil up when idling, while cool plugs would glow red hot at full power and cause pre-ignition. I suspect most modern petrol Vauxhalls have similar requirements, so the plugs are interchangeable. Having said that, plugs are so cheap it's probably not worth the risk.

Omega plugs are the same heat range as those in your Astra.

Bosch & Beru, NGK, Champion etc use different scales for heat.
Most of the Omega plugs were Bosch and 8 on the Bosch heatscale. Approximately equivalent to 5 on the NGK scale. NGK 6 would be approximately equivalent to 7 on the Bosch scale.

I don't believe your NGK plugs are the "100K miles" version. They're standard model Copper/Nickel plugs. The extreme long life plugs will be the multi-pole Beru Platinum/Iridium plugs Z190.

That said if your NGK plugs have truly lasted 103K miles, then I would replace with the same.

[biggriffin]

Every motor I've ever owned, had new plugs every service,.

[STEMO]

Spark plugs, eh? Complicated stuff.

[Nick W]

Every motor I've ever owned, had new plugs every service,.

exactly

[terry paget]

I've put Omega plugs in all sorts of cars without issue  if they fit they've always worked

Interesting. I was taught that plugs with too hot a heat rating would oil up when idling, while cool plugs would glow red hot at full power and cause pre-ignition. I suspect most modern petrol Vauxhalls have similar requirements, so the plugs are interchangeable. Having said that, plugs are so cheap it's probably not worth the risk.

Omega plugs are the same heat range as those in your Astra.

Bosch & Beru, NGK, Champion etc use different scales for heat.
Most of the Omega plugs were Bosch and 8 on the Bosch heatscale. Approximately equivalent to 5 on the NGK scale. NGK 6 would be approximately equivalent to 7 on the Bosch scale.

I don't believe your NGK plugs are the "100K miles" version. They're standard model Copper/Nickel plugs. The extreme long life plugs will be the multi-pole Beru Platinum/Iridium plugs Z190.

That said if your NGK plugs have truly lasted 103K miles, then I would replace with the same.

Thanks for that. May I take it that the 5 in the NGK label NGK R ZFR5F was the heat rating? I note Haynes prescribes Champion RC 10MCC R6 plugs for the Astra 1.4 and 1.6 normally aspirated, NGK IFR7X-7G for the 1.4 turbo, and NGK ZFR6BP-G for the 1.6 turbo, very specific.
The plugs I removed were well eroded, and I imagine were original. As said before, modern cars are wonderful. The Senator was not so good, electronic ignition, but with a distributor at the front behind the open cheese grater grill, which allowed the rain to blow in.

[Enceladus]

May I take it that the 5 in the NGK label NGK R ZFR5F was the heat rating? I note Haynes prescribes Champion RC 10MCC R6 plugs for the Astra 1.4 and 1.6 normally aspirated, NGK IFR7X-7G for the 1.4 turbo, and NGK ZFR6BP-G for the 1.6 turbo, very specific.
The plugs I removed were well eroded, and I imagine were original. As said before, modern cars are wonderful. The Senator was not so good, electronic ignition, but with a distributor at the front behind the open cheese grater grill, which allowed the rain to blow in.

That's right the '5' on the NGK is the heat rating.
As I see it the Vauxhall EPC lists two possible factory fit plugs for your 1.6. Bosch FQR8LE2 and Champion RC10MCC (aka OE198/T10). These and your NGK ZFR5F are all equivalents and are single pole Copper/Nickel. However they all use different heat scales and counter intuitively a lower number is hotter on the NGK scale. Hence Bosch 8 <=> Champion 10 <=> NGK 5. It's never a precise equivalence.

The turbo plugs are colder and are Iridium and Platinum.

So likely somebody changed the plugs in your Astra for the NGKs some time ago. Seems probable they were not factory fit but aftermarket.

I wish I still had my Senator.