Bad smell

As a rider if you get in a car that smells offensive how do you know if it’s the car or the driver? If it’s a recent passenger I don’t want to rate the driver badly and hurt their reputation, but how do I know if it’s really the driver or the car. 🥲 I feel like if I smelt badly it would be an instant 1 star review. Is it acceptable to rate 4 stars for smell?