petrel / petrol are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
petrel: (noun) relatively small long-winged tube-nosed bird that flies far from land.
petrol: NA
petrel: NA
petrol: p·EH·t·r·ow·l
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)