Hotter spark plug?

The Chilton's manual says to run a hotter plug for stop and go driving. The guy at AutoZone didn't have a clue. I run Champion rc12lyc's now. Just looking for a little better gas mileage. Anyone know the number for a hotter Champion plug?

Thats a bad deal for towing and freeway ops in my exp, the plug tip heats up and tends to cause pinging. I dont think it will make enough of a difference to matter. Might be able to cross NGK`s stuff, the lower the # the hotter the plug BPR6ES = hot compared to BPR8ES.

Don't change heat ranges just because you THINK you need to. You need to inspect the plugs and see how they are burning. Having said that, I agree with dyna that 1 range hotter or colder will probably not make too much difference.

The 12 in your spark plug # is the heat range. For Champion's a higher # is a hotter plug; a lower # is a cooler plug.

The only reason I went hotter was to pass emissions. My NOx and HC were both high so I adjusted my MAP to higher voltage to increas my HC then put in the hoter plug (splitfire std replacement). Passed well within limits.

sjx40250 said:

The only reason I went hotter was to pass emissions. My NOx and HC were both high so I adjusted my MAP to higher voltage to increas my HC then put in the hoter plug (splitfire std replacement). Passed well within limits.

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Great but your probably burning your valves or even your piston tops.

BTW Hotter plugs don't mean hotter spark, all it means is they stick in farther and get heated up more to burn off more oil deposits, nothing more.

langer1 said:

Great but your probably burning your valves or even your piston tops.

BTW Hotter plugs don't mean hotter spark, all it means is they stick in farther and get heated up more to burn off more oil deposits, nothing more.

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Just to clarify, a hotter plug doesn't mean the tip sticks out further into the head. The overall tip depth doesn't change - the ceramic insulator design does. The gap between the insulator and the metal casing on a hotter plug has a deeper recess which slows the heat flow away from the tip. Slower heat conduction from the tip means it stays hotter. More insulator material or less recess draws heat away faster. The size of the electrode makes a difference too.

The only reason to change the heat range is if you are having problems with plug fouling from it being too cold and unable to self clean, or pinging from it being too hot and caused pre-ignition (pinging). Going too hot can actually cause the plug tip to melt.

I agree with Saudade. Don't change it unless you have a good reason to. Chiltons is a lousy reference and I wouldn't change plugs based on its recommendation. Heat ranges between different manufacturers vary as well. If in doubt, they cross reference you to a colder plug. Particularly the specialty gee-whiz novelty plugs whose manufacturers don't make as many heat ranges. I think this is why some people have issues with specialty platinum plugs.

As an example, one day I cross referenced the stock Champion plugs to an autolite, crossed that number to an NGK, crossed that to another brand, and then looked that up in a Champion cross reference. The last cross reference was for one heat range colder.


-Chris

thesauceman said:

The Chilton's manual says to run a hotter plug for stop and go driving. The guy at AutoZone didn't have a clue. I run Champion rc12lyc's now. Just looking for a little better gas mileage. Anyone know the number for a hotter Champion plug?

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If you've got a Chilton's manual, look for a few glossy colour pages with pix of spark plug tips - they'll tell you how to "read" plugs, so you can see if you actually need to go to a hotter/colder plug.

I've been running AP3924 (Autolite Platinum @ specified heat range) in all of my RENIX rigs without trouble - with a pretty good mix of stop-and-go, highway, short haul, long haul, and sitting and idling. I check them once a year (haven't had to replace them yet) for signs of trouble, and haven't seen any yet. The oldest ones have been in service for five years.

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