Final answer:
The sentence 'Oscar noted that on the car journey from his house to his Grandparents' house, he could watch 4 episodes of his favorite cartoon' uses hyperbole to exaggerate the length of the trip.
Step-by-step explanation:
The literary device used in the sentence 'Oscar noted that on the car journey from his house to his Grandparents' house, he could watch 4 episodes of his favorite cartoon.' is a hyperbole. Hyperbole is an exaggeration that is not meant to be taken literally and is often used for emphasis or effect. In this case, the statement likely exaggerates the length of the car journey to highlight that it takes a considerable amount of time, enough to watch several episodes of a cartoon.