Topic: Why do spark plugs sometimes only color on half the insulator?

[manjisann]

I pulled the plugs during lunch at work and at least one of them has black on only about half the insulator running lengthwise, what causes this? The other half is whiteish. I know I've seen pics of this on here in other posts, but couldn't find any. If needed I can try and take pics later when I get home.

Thanks,

Brandon

[Don R]

Cylinder turbulence and the direction of the ground strap probably have a lot to do with it. Unless you index the plugs the ground strap location is not consistent.