E3D hotend temp swing of 10c (+-5c)

So I'm getting about a 10c swing on my hotend during prints from it's low to hi point... about -5c to +5c.

The E3D hotend is using the same type of thermistor I initially had in the stock hotend. It's attached into the E3D with copper high temp RVT gasket material. I'd had the problem before, so figured I must have screwed something up. I pulled the thermistor out, removed all the RVT from it and the hotend, and reinstalled. Same problem. I don't know if it's just what E3D's do, if I've got some setting set funky in the firmware, or if I shouldn't be using the RVT to attach the thermistor into the hotend.

Any ideas here on what might be going on, or is this just to be expected with the E3D?

 

I'm getting a 1-3 degree swing(total) on mine. RTV always. Several thermistors along the way and pretty consistent in that range. More importantly, does it affect your print in any way? If not, it isn't a problem (in my book, anyway).

 

I use Mega Copper Gasket maker and the E3D semitec thermistor. I see almost no temperature variation. I did do the PID calibration procedure but I'm not sure it made a difference.

 

Does anyone know if silicone thermal grease is stable at our extruder temperatures? I was going to put a drop of grease on the thermistor before sealing it up but started wondering about this. Normal max integrated circuit temperatures are much lower than our roughly 180C to 240C range. I had a hard time finding a max spec for a normal silicon/zinc oxide grease. Artic silver which is not silicone based lists a "extended temperature peak" of 180C and "long term" of 130C. http://www.arcticsilver.com/as5.htm . A high-temp paste from Omega lists a 200C max continuous.

So we might want to be careful with the exact type of thermal grease we use. Some random stuff from RadioShack might break down and over time.

 

I used Logisys Deepcool Z5, it's stable up to 300c.

 

Thanks! Found on Amazon prime:
http://www.amazon.com/Deepcool-Thermal-Bonding-Grease-Compound/dp/B004X7XSVY