Octane rhymes with:
lamountain, ramtane, baudoin, boatswain, chapdelaine, chilblain, cyclohexane, duplechain, finucane, hexane, ibogaine, lamountain, madelaine, moscowane, ptomaine, ramtane, tremayne
Octane sounds like:
o'steen, ogden, ossetian, osteen, osten, ostin, ostman, oxdon, oxidation, oxidyne, oxton