Well
1st its a .co.uk and as far as I am aware, Opel is not the name of that car in the UK, so that makes is useless as a .co.uk if your meaning the car name. (they are Vauxhalls here in the UK)
2nd TM issues if you relate the name to the opel cars, you wouldnt be able to sell accessories for opel cars if you used it.
But, you might get away with it if you made an informational site on the models of Opel cars and promoted them via it, without making yourself any money off it. In which case the name would still be worth reg-fee, no one wants a name you cant make profit on.
Else reg-fee anyway if you can find a buyer.