Weird, I could swear certain RC fuel companies were using both....
i've heard that many years ago but a couple people but then when they checked their source it was no longer available. I'm sure you can still find it at some RC company somewhere, perhaps a custom blend then you'll have to distill out the NE.
as far as i know though, fuel with a mixture containing NE fell out of favor a long time ago and is very rare/difficult to find