Changed plugs this morning after gradual decline in performance. Mileage seems to still be good. But don't wait this long or they may become a permanent part of the head as the threads were quite rusty - given the amount of alcohol and water in the gas these days.

 

" given the amount of alcohol and water....."

Unless you have a major compression problem with your engine(excessive by-pass thru the thread area)you shouldn't have any fuel, water or alcohol on the threads of the spark plugs. The rust and corrosion is a result of dissimilar metals and external moisture.

 

Time machine!

 

I split this off from the original 5+year old thread, just to let y'all know, that way donbrew's comment won't seem utterly out of context.

aboard mjhhr!

As Snoopy stated, you really shouldn't see rust on the plugs. Carbon accumulations, yes, but not rust unless there's a situation where coolant is finding its way into the cylinders...or if the plugs that came out weren't the proper AC Delco 41-103 Iridium models.

 

And a coat of never seize on the threads to prevent galling