Walter and Group, Bosch told me today that the Plat + 4 is a medium heat range plug = to the a HR8 or HR9. The HR6 as the car comes with is the coldest burning plug for this series and for short drives a hotter plug would burn better. That's why I ordered in 3 sets of ea range to run my test with them, but as robert has pointed out with his experiment it sounds like Plat + 4 is the way to go. As to copper, silver, or platinum, i think is just resistance factor for more critical applications that we don't have. What do yall think. John www.specialTauto.com --- In dmcnews@xxxxxxxxxxx, "Walter" <Whalt@xxxx> wrote: > So which plug is better for the Delorean? Bosch Coppertip, Bosch Platinum+4 > or Bosch w/silver electrode?