NGK Spark Plug Chart
The information below was taken from a pamphlet given out on NGK Spark Plugs in the late 1970's, it is just as valid today as it was then.
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1 Oil Fouled |
2 Oil Fouled |
3 Carbon Fouled |
4 Too Cold |
5 Too Cold |
6 Cold or Rich But OK |
7 Cold or Rich But OK |
8 Cold or Rich But OK |
9 Good |
10 Good |
11 Good |
12 Good |
13 Real Good |
14 The Best |
15 Best |
16 Best |
17 Best |
18 Good |
19 Good |
20 Good |
21 Kinda Hot But OK |
22 Hot or Lean But OK (?) |
23 Hot or Lean But OK (?) |
24 Hot or Lean But OK (?) |
25 Too Hot or Lean Pre-Ignition Range |
26 Too Hot or Lean Pre-Ignition Range |
27 Too Hot or Lean Pre-Ignition Range |
28 Too Hot or Lean Pre-Ignition Range |
29 Too Hot or Lean Pre-Ignition Range |