Originally Posted by djb
Originally Posted by WyrTwister
I pretty much replace the spark plug and change the oil on our mower each spring . And often replace the air filter . All as preventative maintenance .
Replacing the spark plug annually is usually pointless. It's a routine from over a half century ago, when spark plugs wore out. Utility spark plugs are built with the same technology as automotive plugs, which have a typical 100K or 120K replacement interval and a wear life of double that. The 25 hours annual use for a typical mower is trivially small in comparison.
The mower pictured must have been running pretty rich with the "100% natural pre-filter", but the plug was still working and likely cleaned itself with a few minutes of normal running.
Yep. I stopped replacing plugs in my personal and resale equipment. Inspect, clean, gap. Send it.
Only replace them if they are visibly shot.