Originally Posted by Chickentrader

I don't understand why it recommends 7 plugs for conditions that cold, and I haven't noticed that on the website. F stands for "Fredda" and H stands for Hot (same as C), and the difference is the thickness of the plugs body. The plugs with cold thermal range F, have a body with thinner walls and shorter body, so they dissipate heat better and faster to the engine head.

According to the information that I have 7H plugs are for much warmer weather than that. You can check the file attachment for the information that I always have referred to. I hope that anyone that disagrees or have better information will share it here, so we can all learn.