NGK G-Power Spark Plug vs DENSO Iridium Power IK20 Spark Plug

These two plugs do not fit the same car, so the choice is decided by thread size first. The NGK G-Power is an M12 plug with a 1.043 in reach; the DENSO IK20 is an M14 plug with a 19 mm reach. For a car that takes the DENSO fitment, the IK20 is the stronger performer: its 0.4 mm iridium center electrode and U-groove ground give sharper response and better acceleration than a standard plug, and owners report long service life. The G-Power is a sensible, durable platinum replacement for stock double-platinum plugs, but it is a value-oriented plug, not a performance step up.

• Choose the NGK G-Power if your engine takes an M12 x 1.25 plug with about 26.5 mm reach and you want a durable platinum replacement for stock double-platinum plugs.
• Choose the DENSO Iridium Power IK20 if your engine takes an M14 x 1.25 plug with 19 mm reach and you want sharper throttle response and stronger acceleration from a fine iridium electrode.