spark plug heat range explanation

[16gauge]

I used to know this and still should, but alas....other issues in life tend to displace things from 20 years ago. Please tell me about which number is hotter or colder and why I should care... the numbers 6,7 and 8 seem to be really close/interchangable...thank you for your opinions..

 

[TimberPig]

You need to give a plug make as well , because in some makes (like NGK), smaller numbers are hotter, and in others (like Champion), larger numbers are hotter. Basically the colder plugs conduct the heat away from the plug nose more quickly than do the hotter plugs, mostly due to how far the plug nose projects into the cylinder and by construction differences.

 

[16gauge]

Thanks TimberPig, do you know about Bosch... they seem to have a whole different numbering system.

 

[Simonizer]

Thanks TimberPig, do you know about Bosch... they seem to have a whole different numbering system.

I will bet you need a WSR6F if you have a Stihl or Husq. Other than that, I don't really know stuff about things. Cheers.

 

[16gauge]

Thanks Simonizer.

 

[Diesel JD]

I've run Champions in my STihls with no ill effects. Boash work good, champion work good, just keep decent correctly gapped plugs in it. That siad, I will believe that the Stihl system was probably designed with the WSR6F or WSR7F in mind

 

[16gauge]

Thanks Diesel...I'll have to check the shop tomorrow morning...I've got two plugs pulled from Stihl saws, an 031 av electric and nephew's 029. They have wierd numbers on them. Like (guessing) 793 and 1042 or something. Sorry for not being prepared with the actual numbers. I'll post them in the AM.