And when such different conditions do occur, the stock spark plug are no longer the adequate.

If the spark plug results colder than neccesary, the combustion deposits will not burn and will stick to the spark plug, fouling it, and since carbon is an conductor of electricity, it would deflect the electricity to the ground instead of creating the spark, resulting in engine misfiring. The unburned fuel washes the piston rings oil in the cylinders affecting dangerously the engine´s lubrication with what wears out prematurely the rings, the pistons and the cylinders.

And if the spark plug results hotter than necessary, the engine would overheat, blowing the cylinder head gaskets, wearing out the piston rings, and another severe damages, even generating pre-ignition or detonation, burning valves and making holes in the pistons.

So, application charts that actually don't indicate the right spark plug for each of these conditions or to the possible different combinations thereof, are no longer the adequate guide for the selection of the appropriate spark plugs for each particular case.

You dont´have to take our words. Spark plug manufacturers have never failed to explicitly acknowledge that: