John James Gold'n Glide Milliner's size 10. It has a gold eye making it easier for me to see to thread the needle. It's also Teflon coated so I can push it through the fabric easier. I use those with Aurifil 50wt thread (2 ply).
I agree with bjchad that an 8 is really quite thick for doing needle turn. A 10 or 11 would be better. Maybe consider investing in a needle threader. Silk thread is wonderful & super fine, but having to tie it onto the needle every time is more work than I'm usually willing to do.
EDIT: Sorry, just read that you were using some kind of threader. Wanted to point out that John James makes needle theaders for their needles. I haven't used them very much, but they worked well the few times I've needed them (mostly back before I bought better lighting for my studio space).