This was the first car owned by the family. Vernon drove this car to work on 1 November, 1981. On this day Vernon saw a number of unusual things travelling to and from work.
At the beginning of the summer holidays, Vernon acquired a brand new company car. While the Dursleys stood outside "loudly" admiring the new car, Harry was able to use this time alone in the house to sneak some of his spell books out of the cupboard that Vernon had locked them in. Presumably this was the same car that the Dursleys, along with Hestia Jones and Dedalus Diggle, used to depart from 4 Privet Drive for the last time on 27 July, 1997.
Behind the scenes
The Dursley's car in Deathly Hallows, a black 2008 Vauxhall Vectra Sedan
In all three instances, the cars are taken from a timeline which considers the film's release date as the present day. This means that using the original timeline, they are all anachronisms, as none would have been available at the actual date.
