There's been PLENTY of talk over the years about spark plugs.... and their cost.
While Mercury's plug are indeed more expensive- they come with a ONE YEAR PARTS AND LABOR WARRANTY. What this means- is that if the plug comes apart- and it's the right plug, you have the ENGINE MANUFACTURER standing behind that plug.
If you're price shopping.... PLEASE, PLEASE buy ONLY the recommended spark plug.
For those of you under warranty- remember, that although the engine manufacturer cannot void your warranty for use of an aftermarket product (see the Magnuson Moss Warranty Act of 1976)... they DO have the right to DENY a warranty claim if that aftermarket product "contributed to, or caused a failure".
The pictures below are from an Optimax that ran an "aftermarket equivalent" (term used very loosely) spark plug with a name similar to "car-o-light" for less than 10 minutes... the plugs OBVIOUSLY were not even remotely "equivalent" (not even the correct heat range or reach):
The above pretty well negated ANY potential savings.... preignition/detonation resulting in hot-spots near the edge of the piston dish resulted in catastrophic piston failure.![]()