Lets start with the fact that glow plugs confuse me. There are are so many on the market (hot, medium, cool, etc.) and OS makes enough to help with my confusion. I need to purchase some for my .61 FX. I use either 10% or 15% nitro fuel. I looked at the manual and it listed the #8, A5, and A3. In the tower catalog it mentions there is also the P series plugs. What should I purchase? Also, any info on how to understand the various plug designations would be helpful.

For the O.S. Max .61 FX engine, your best bet is the O.S. #8 or #A3 plug. The #8 is just about the finest general-purpose glow plug you can buy, and the #A3 is similar but a bit lower in cost. When in doubt, go with the #8. It's about all we used here in the service department.

Thanks Bill. I will place an order right now.

Patrick