Ricin
Ricin is a poison found naturally in castor beans. It has a very distinctive odor.
The reason it's put in there is to give the oil the fragrance of Castrol R,which is a castor bean oil used by racers back in the old days.
(Castrol=castor oil)
Before synthetics,it was the only thing that would keep a big 4 stroke single,such as a Norton Manx,or BSA Goldstar alive through a 500 mile race.It was also the preferred oil for pre-mix two strokes.
Even on 4 strokes,you could smell the bean oil in the exhaust.
That ELF oil probably works fine,but I wouldn't waste my money on it.If you want the smell of Castrol R,just get a can of it(it's still available),and mix a little in your gas.
By the way,a few pages back I posted that I use Castrol R in my bike.That was a JOKE! Don't put that stuff in your engine.It's a one time use,non detergent oil.After it's heated,it cools down into a sticky congealed mess.It would probably ruin your clutch immediatley,and what it might do to the gearbox,I don't want to think about. I should have been more clear.Sorry.
Ricin is also used in biological weapons.
Cheers!
Bruce