Reading Spark Plug: Black 'Soot' Color
I did a little basic (near) end of season maintenance to our old ~1986 Murray 20" push mower with B&S 3.5HP (92502). Pulled the plug to replace since it's been about 5-ish years since it was installed.
The old plug had a flat black sooty coating on it. There was actually minimal 'wear' to the plug as far as the tip, gap or gnd electrode.
Q: What if anything should I look for to better optimize engine performance/life?