Who owns the car, if it was bought together it will be half his in relationship property.
We put ours on our mortgage & then when we split relationship property I had to pay him for half of the car as I retained use of the car for the kids. Even though he had a company car that cost him nothing I still had to pay out half.
It was a stationwagon & the petrol price was huge & I have since downgraded to what I call a "nana car" which doesn't cost much to run.
If the car is in your name & you can prove it in court then change it now, otherwise I would wait.