Paul, was hoping musky or one of the the other tech proficient would sort it out for you. In the meantime why not use a stright 4o wt until you decide ,castrol or Morris oils are okay but any reputable name will do . about £16 per 5 ltrs.
Musky, interesting aside about castor based lubs, during ww1 all allied pilots on rotary engined planes always sufered from the trot's big time due to inhaling and ingesting the castor oil from the engines virtual total loss system ,so don't put to much in or you could cause any township you roar through to have to run for the loo's, ha ha , regards BobH