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Pmag. Use of 100LL which auto spark plugs to use

C

CFItom

Member
I recently bought a thorp T18. Dual Pmags. The previous owner was using 100LL exclusively. He also was using NGK Iridium BR8EIX (5440) plugs using plug adapter. I priced locally at $13.29 per plug

Another dual PMag user states he uses Autolite 386 that do not need thread adapter and claims these run under $5 each. And he replaces all each annual since it is so inexpensive.

What is the advantage of using the more expensive iridium plugs? Is it worth 3 times to cost? Are iridium plugs better when burning 100LL exclusively or primarily versus unleaded auto fuel?

This is for a Lycoming O320b1b putting out 160 HP.
 
I've used all three. Least time on the NGK iridium. Had one NGK BR8ES fail over 12-14 years recently. I've noticed no significant engine performance difference with these various plugs, but I haven't studied closely. AFAIK, the 100ll usage isn't a big deal. But that's all I've used with Pmags. Haven't noticed exceptional fouling or other impact.

Last, watch for counterfeits. I source only from reputable auto supply stores. Last plugs I bought from Advance Auto Parts. Cost $8 for 2-3 hour delivery to my home!
 
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Iridium aviation plugs are reported to last at least 1200 hours. I would think the auto plug versions would last a similar amount of time. The biggest problem I see; is the gaskets are not removable on most auto plugs, we remove them every 100 hours or so for a look and regapping as needed. The gaskets might not be up to sealing well after a few cycles.
 
BoydBirchler said:
Iridium aviation plugs are reported to last at least 1200 hours. I would think the auto plug versions would last a similar amount of time. The biggest problem I see; is the gaskets are not removable on most auto plugs, we remove them every 100 hours or so for a look and regapping as needed. The gaskets might not be up to sealing well after a few cycles.
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Do you remove the auto gasket and then replace with traditional aviation copper gaskets?
 
I haven’t used copper gaskets. I like the idea though….
EDIT: On second thought I don’t like the idea. Would likely change the reach.
I use the iridium BR8EIX on my bottom plugs only. I oil fouled a standard plug on the bottom once. I let them go about 300 hrs before swapping them out.
 
DCBrown198 said:
I replace the copper gaskets between the adapter and the cylinder head surface.
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I think I may have misunderstood your original response. When you said you remove “them”. I thought “them” meant the auto plug gasket. But ai think you meant that you remove the plugs themselves.

Are automobile compression psi higher than on an O320 at 8.5 or 9 to 1 compression ratio? Of auto compression is higher. Why would the auto gasket fail? Other than in aircraft we remove the plug at annual co Siri on for a leak down compression check. Whereas in an auto they are install and forget until some day years in the future you remove and replace them.

If the iridium last three times as long and cost three times as much. It is the same cost at the end of the day.

Maybe going with the standard autolite plug and change at annual condition every year makes sense. That way the auto gasket doesn’t wear out with essentially in once and throw away. If they are really $3-$4 each then it is disposable more or less.
 
Tempest fine wires went 2000 hours and were still serviceable when engine pulled and sold for drone work. Run WOTLOPSOP its whole life. It is possible the NGK iridium plugs would do the same but they are a lot cheaper for sure.

In flight mag check prior to TOD will find most plug issues long before they become a problem you will find on the ground. DO THEM every flight.

 
RV10inOz said:
Tempest fine wires went 2000 hours and were still serviceable when engine pulled and sold for drone work. Run WOTLOPSOP its whole life. It is possible the NGK iridium plugs would do the same but they are a lot cheaper for sure.

In flight mag check prior to TOD will find most plug issues long before they become a problem you will find on the ground. DO THEM every flight.

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I am not familiar with the acronym TOD!

What will the EMS show if there is a problem?
 
ATC_RV8OR said:
They're less than $3 at Rock Auto for the regular BR8ES. At those prices change them when you change your oil. Why bother gapping cleaning? Remove, observe the burn colors and toss.It was the Autoolite 386
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It was the Autolite 386 standard plug that is $4 reportedly. Not the NGK Iridium plugs. They are like $13 each.
 
CFItom said:
I recently bought a thorp T18. Dual Pmags. The previous owner was using 100LL exclusively. He also was using NGK Iridium BR8EIX (5440) plugs using plug adapter. I priced locally at $13.29 per plug

Another dual PMag user states he uses Autolite 386 that do not need thread adapter and claims these run under $5 each. And he replaces all each annual since it is so inexpensive.

What is the advantage of using the more expensive iridium plugs? Is it worth 3 times to cost? Are iridium plugs better when burning 100LL exclusively or primarily versus unleaded auto fuel?

This is for a Lycoming O320b1b putting out 160 HP.
Click to expand...
I’ve been using Autolite 386 plugs for couple hundred hours. Dual pmags w O-320 160hp. No issues.
 
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