"Yo tengo un carro viejo."
Translation:I have an old car.
The only difference is they're used in different places. Coche in Spain, Carro in Latin America.
Also carro in Spain is for example what farmers used to tie to horses for them to pull it, and in Latin Spanish means car. In Spain car is named coche.
When are the bosses at DL going to clear up this confusion? The Castillian Spanish (proper Spanish) word is COCHE. The South American word is CARRO. As we are supposed to be learning Castillian Spanish, since the DL "upgrade" a few weeks ago there have been numerous SA words introduced - all they do is confuse ! 20th Sept 2018.