Sewers aid is what I use. Sorry and I see others have answered for me. Thank you. Been gone... I only use it prior to starting with it but if you will be sewing a lot then adding some more would help.
http://www.sailrite.com/Sewers-Aid-L...&category=7273
Here is a site you can go and see what the product looks like. I have used it in my bobbin without having any issues. The only thing that might be an issue is if you iron over the thread. You could melt it.