Was watching the classic film "American Graffitti" last night and in the beginning when Ron Howard'* character, Steve, leaves his Chevrolet to "Terry the Toad" ( played by Charles Martin Smith) to take care of until he gets back from college for vacation, he leaves instructions written and left in the glove compartment for the proper care of his beloved Chevy while he'* away - one of which was to specifically use only "Castrol weight 30 R" oil.

My question is what type of oil is 30R and is it still in use today?

Probably some varation on monograde 30 oil. Monograde oils are still around today and are mainly used in small air cooled motors(lawn mowers go carts). Crazy old people will sometimes want to use them in old cars too because they think the oil will keep the engine from leakign or burning oil.