Tenses

English as a Second Language English Vocabulary, Grammar and Idioms
1

Background: I bought a new car yesterday.

  1. My car is expensive.
  2. My car was expensive.
  3. My car cost a lot.
  4. My car costs a lot.

Which is correct?

Many thanks.

2

All are possible, but these are preferable as they are related to the present:

My car is expensive.
My car costs a lot.

3

That’s not quite right. There is no ‘preference’ because they are related to the present. It all depends on context.
If you are speaking about the time when you bought the car, then ‘my car was expensive’ and ‘my car cost a lot’ are the correct forms and the other forms are incorrect.
If you are speaking about your car generally, compared to other cars, then ‘my car is expensive’ and ‘my car costs a lot’ are the natural options, though all are possible.