Surrounding the center electrode, which contains 75% more platinum than previous Bosch platinum plugs, are four "surface air gap" ground electrodes made of a special wear-resistant nickel yttrium alloy. The angle and position of the four electrodes creates multiple spark paths that cause the spark to jump sideways. This has a self-cleaning effect on the center electrode and results in a longer, more powerful spark that reduces misfires for improved engine performance, better fuel economy, lower emissions and faster acceleration.
When these spark plugs fire, the spark jumps randomly to any one of the four ground electrodes. It does not jump to all four electrodes at the same time. This spreads the wear across four electrode surfaces instead of one as is the case with a standard single ground electrode spark plug.
Bosch says their tests have shown the new Platinum +4 plugs can improve fuel economy up to 4.8% over other competitive spark plugs. Fouling resistance is also said to be 33% better.
Though Bosch makes no specific mileage claims for their Platinum +4 spark plugs, they do say the plugs meet or exceed OEM requirements for 100,000 mile replacement intervals. Bosch says the plugs show almost no increase in firing voltage requirements after 100,000 miles of operation. Bosch has also run tests where the plugs have gone over 150,000 miles with no appreciable wear, so these would seem to be lifetime plugs for many vehicle applications (unless, of course, the engine is burning oil, in which case fouling might occur).
Another unique feature of the Platinum +4 is that the surface air gap between the center and four ground electrodes is factory present to 1.6 mm and is nonadjustable. No attempt should be made to adjust or change the air gap when the plugs are installed, even if the air gap specification is different from that specified for a standard spark plug. The wider gap of the Platinum +4 is necessary to achieve the advantages above.