"My uncle's car is smaller."
Translation:O carro do meu tio é menor.
Yep! In spanish we say "más pequeño",not the same in Portuguese. We say "menor" (smaller), "maior" (bigger) (menores, maiores = plural form. They're used for both masc or fem.)
Where I live in Portugal "mais pequeno" is used for "smaller", and "menos" for "less". We are close to the Spanish border though, so not sure what is more common in the rest of the country.