Home › Forum › Ask A Member › Champion 4K spark plug question › Re: Champion 4K spark plug question
August 3, 2016 at 6:48 pm
#41537
By my old plug chart, 7 is replaced by D9 and 9 is replaced by D21 Or in other words the numbers in order of heat range (hottest first) are:
D23
D21 (old 9)
D16
D14
D10
D9 (old 7)
D6