In the US, we would say, "Whose car is this?" I don't think that "Whose is this car?" is incorrect. But in the US, it would sound extremely formal and even antiquated (old-fashioned).

Hi GGabu The formal question would be "Who does this car belong to?" However many people just use "Whose car is this?" which is a more general, casual form of speaking. One could also say "Who owns this car?".

Soy de Irlanda del Norte y las dos maneras me suenan igual de bien

It does relay the question, however is not something commonly used here in SA.