veggie oil premix

not a great idea man.
Castrol R etc are Castor based, so you could say it is veggie oil, but they contain high levels of phenol molecules which are attracted to really hot engine parts.
Burnt phenols smell sweet, which is why Castrol R smells sweeter than TTS or Motul 800, which are synthetic based. They just cant replicate the tiny phenol molecules as well as Castor plants grow it.
However veggie oil sucks up moisture out of the air so it's best to drain the tank after every race.
I bet your fryer oil smells like **** when burnt, i.e. no phenols.

There is always grey area to questions like this. I knew a guy many years ago that ran unused veggie oil in a old Yamaha enduro for a few years...seemed to run fine. It was his old mans bike and he didnt have the money to spend on 2 stroke mix. Of course, he wasnt revving the bike to the moon. For our moderate paced trail ride, it worked. Would I put veggie oil in a new Honda Service CR500....NO.