Help with choosing spark plugs for V8 HO with LPG

[turbomart]

Using a regular plug vs platinum will not harm any engine. Platinum is used because its harder wearing and lasts longer. The heat range is important, detonation is what harms a motor and to hot a plug can lead to pre-ignition. The other important thing is the fuels octane rating, higher octane fuels are less likely to suffer from pre-ignition.
Higher compression engines also generally require higher octane fuel.
So in conclusion , HO motor needs pulp fuel but ordinary s/plugs are fine.
Lpg needs more spark energy hence smaller gap and is higher octane but due to lack of cooling effect can benefit from slightly colder plug.

Btw, I have read that upper cyinder lube is recommended with this motor so I am running it. I have first hand experience with the effectiveness of upper cyl. lube and recommend it with the 4.7L.

Thanks for all that info; it's encouraging that I was told the same thing.
I run 98ron petrol in all my cars and installed a Flashlube kit in the Jeep.

And I bet if you worked out the plug cost per km I wouldn't be surprised if it worked out so close it doesn't matter. The important thing is to check and replace the plugs when they're due.

[Hanna]

Yep turbo is on the money again - smaller gap and colder plugs help with LPG and platinum plugs help with longevity.

I have been running the NGK ZFR6F-11G in my injected LPG (non-HO) for 6 years and 80,000km without issue. You just need to re-gap every couple of services (5,500km is way too soon if you ask me - even for a routine service 10,000km is fine - but it can't hurt to check them regularly if you're that keen to do the pain in the arse job!) and replace them at around 25-30,000km if required.

Also, there's no need to run Premium ULP in an engine unless it's specified by the manufacturer or the compression ratio has been raised from factory specs. All the higher octane rating does is increases the resistance of the fuel to burn, reducing the chance of pre-ignition and subsequent detonation of the engine.

Unfortunately running Premium ULP in a low-compression engine is a complete waste of money I'm afraid.

[turbomart]

Yes agree Hanna but have noticed some light pinging when towing on hot day running ulp, US rate there fuel differently and it seems our fuel is a little lower spec.
Chuck a little 95 octane in the tank and its fine or just be mindfull and back off in those conditions.