octane rating vs quantity

octane rating and quantity both are nouns.

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

As nouns, quantity is a hypernym of octane rating; that is, quantity is a word with a broader meaning than octane rating:

octane rating: a measure of the antiknock properties of gasoline
quantity: how much there is or how many there are of something that you can quantify

Other hypernyms of octane rating include amount, measure.

octane rating (noun)	quantity (noun)
a measure of the antiknock properties of gasoline	how much there is or how many there are of something that you can quantify
	an adequate or large amount
	the concept that something has a magnitude and can be represented in mathematical expressions by a constant or a variable