OS and Turbo glow plugs go grayer sooner(easier) than Mccoy,traxxas or fox plugs; this does not make them bad glow plugs.

            Actually when "A" new plug wire just goes slightly gray after a 5 or 10 minute hard run it means your very close to an optimal horsepower tune.

READING YOUR PLUG:

1} Wire and surrounding bottom of plug wet, with like new shiny wire = rich side of optimum power

2} Wire and surrounding bottom of plug starting to dry and wire starting to gray = very close to optimum power

3} Wire and surrounding bottom of plug dry, wire totally gray but not distorted optimum power

4} Wire and surrounding bottom of pug dry, wire distorted = slightly lean "DANGER!"

5} Wire and surrounding bottom of plug dry, wire broken and distorted or burnt up = extremely lean possible engine damage!

Note: You can only "read" your plug in a nearly new state(Wire like new and shiny) A gray plug can still operate good. A fter a plug has gone totally gray, engine performance can suffer greatly. To test the plug put in a new "GLOW PLUG" and if you do not notice a difference in engine performance then save the gray plug or put it back in the engine and run with it.

"MOST IMPORTANT"

If your engine does not feel or run right try a new glow plug before making any major tuning changes!