octane number vs octane rating

octane number and octane rating both are nouns.

Word	Noun	Adjective	Verb	Adverb
octane number	Yes	No	No	No
octane rating	Yes	No	No	No

As nouns, octane number and octane rating are synonyms defined as:

octane number and octane rating: a measure of the antiknock properties of gasoline

octane number (noun)	octane rating (noun)
a measure of the antiknock properties of gasoline	a measure of the antiknock properties of gasoline