Marty, if your engine 'ran fine' on the OS #8 then just stay with it. The OS #8 is a med-hot temperature range plug.
The best way to see if your engine needs a different plug is to see what happens when you remove the power from the plug after the engine is started and running. If the engine is running OK with power supplied, but the rpm sags when power is removed, then the plus is not hot enough. As a rule of thumb, low nitro fuels (and I would consider 8% low nitro) need a hot plug. The OS A3 (A6) is a hot plug.
Due to cost, Brodak sells Fireball plugs for $5 and I have used them with no issues. Fireball makes a hot and medium-hot (what they call standard) plugs.
Also, for a CL engine application, I don't use a plug with an idle bar. Idle bar plugs are intended for RC engines with carburetors where the engine speed is varied. The 'idle' bar is just as stated. Helps keeps fuel off the plug element at idle conditions. Not needed for full speed CL application.
I don't have any insight as to whether the situation with glow plugs will get any better or not. I have a pretty good supply and I'm always keeping my eyes peeled just in case I run across something.
Colin McRae said;
"Also, for a CL engine application, I don't use a plug with an idle bar. Idle bar plugs are intended for RC engines with carburetors where the engine speed is varied. The 'idle' bar is just as stated. Helps keeps fuel off the plug element at idle conditions. Not needed for full speed CL application. "
Some of us use idle bar plugs for a reason. It acts as a barrier to protect the element against debris getting into that chamber and distorting, damaging or shorting the element. It also give carbon a place to form instead of inside the chamber or covering it up as it accumulated. If you fly ringed engines or have any appreciable amount of castor oil in your fuel, it will make carbon when it runs and it will build up where ever it can stick to. I have seen plugs that have been in an engine so long that the opening under the idle bar gets covered up and the engine starts running rough, but the engine would still run. This is usually a gradual process. If the idle bar wasn't there , it would accumulate right over the element in less time. It may chose to quit or really fall of at a bad time, like right before the model reaches the top of the wingover or just as you are finishing the clover!!
In R/C, fuel still needs to reach the element at all times. That is how a glow engine works, a catalytic reaction between the methanol and the metal the coil is made from. Have you even had an engine start without warning before you attached the battery? Happens all the time if conditions are right.
Type at you later,
Dan McEntee