Correct Spark Plugs

[Tony Jordan]

I just put new plugs in my nieces Ford Focus which I thought was a Fusion. I used Autolite xp5363 but when I went to various sites it showed the Autolite app5863. Will it hurt her car and should I take them back out??

 

[Handy Andy]

Well, let's see...

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The two are identical - only the "Gap" is changed.

The 5363 gap is greater - larger, but to help you understand this - requires a bit more physics but the electrode gap is larger meaning it requires more energy to fire - which can lead to mis-fire due to the effects of compression - meaning the air/fuel charge when the compression stroke occurs, may cause the misfire - becasue the larger gap would also look like "wear" of the spark gap of a typical spark plug - it's harder to form the arc when the gap is bigger in compressed atmosphere than it is in sea-level "free air" (10:1 compression versus 1:1 sea level)

So, if you reset the gap to the 0.8mm then you are fine, leave them in.

However, if not - you can make a choice, re-gap or exchange - either way the shop doesn't like taking back used plugs unless they have a strong constitution and are willing to keep a customer happy by exchanging them for another type - of the same brand. Which is why I showed you the Iridium for they can swap part for part due to errors, but not a different construction - for it becomes more of a loss to the cashier due to the error.

Now the APP - for the plug you thought you should use...

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The only benefit I see in using Platinum is in the emission side of things. It's part of the Catalytic converter as processing the burnt fuel by providing a "carrier" as part of the catalyst process of exhaust to O, C and H from HCO in the exhaust itself - helping to break hydrocarbon bonds to revert it back to their basic elements. Iridium is simply a harder metal, so it lasts the longest - at least they claim to have it survive up to 120,000Miles (YMMV)

As you can see, they all use the "same" heat range - so the plugs will survive and not damage the cylinder head or the pistons in any way by dimension or by causing fouling or excessive knock from being the wrong heat range in itself.

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Series 37 refers to construction and it is a "hotter" plug to help burn off the electrode deposits and keep the "soot" that would be left as a deposit from becoming something it can foul on and mis-fire. (again a gapping and debris issue)

This may be more information than you need, but this is to show you, you did not do anything wrong in selecting a longer life plug.

Just the pre-set gap is different - that is up to you.

 

[Tony Jordan]

Many thanks Andy for the reply, after looking everywhere I couldn't see if it was ok to leave them in so I went to her house Sat. and removed them & put the old ones back in till the app5863 come in Tue. I was freaking out that maybe I had damaged the cylinder heads and I knew my status as favorite uncle would turn to Mudd. With your info I'll keep them and gap them to .08 for future use. I appreciate the helpful answer......

 

[Handy Andy]

If you have any questions, just post them here - there are a lot of others that may be able to share some input.

• - but then too, when you need to know, re-check this thread, for it does have the latest information posted for all the world to see at the time the post was made.

So, if you have questions about that "gap" or heat range - it's all here in this thread for you to look back on and do it right for her.