The Bosch 4 design really works. Years ago I had a new 02 Impreza that had a preignition issue under w.o. acceleration. When I used premium gas the problem dissapeared under w.o.a.. Then I changed out the oem champion copper core plugs and put in bosch platinum 4's. This change allowed me to go back to regular gas with no preignition issues during w.o.a.. Bosch is #1 to me.
The Bosch 4 design really works. Years ago I had a new 02 Impreza that had a preignition issue under w.o. acceleration. When I used premium gas the problem dissapeared under w.o.a.. Then I changed out the oem champion copper core plugs and put in bosch platinum 4's. This change allowed me to go back to regular gas with no preignition issues during w.o.a.. Bosch is #1 to me.
Howmushdotheycost