The prediction came as the firm signed off a single-badge deal for its fleet of 2,100 essential user cars worth £27 million at showroom prices.
It said a key aspect of its choice was the quality of lower-medium models available.
Trinity, which publishes both national and regional newspapers, including the Daily Mirror, awarded the contract to Vauxhall after going out to tender at the end of a four-year contract period with previous supplier, Ford.
Trinity's fleet will be managed by East Midlands-based management service provider Business Vehicle Services and run over a four-year/72,000-mile replacement cycle with full maintenance, with several contract hire suppliers.
David Redpath, fleet manager at Trinity Mirror, said: 'We will be using a commercial tendering process with our contract hire suppliers on a periodic basis to guarantee the best possible contract hire rates and keep running costs as low as possible.'
The group will order at least 1,700 Astra SXi 1.7 CDTi vehicles as the mainstay of its fleet, while it also expects to order between 400 and 500 Vectra 1.9 CDTi models.
Redpath added: 'We found with our previous supplier that a number of our drivers in high job grades chose to downsize to a smaller car and benefit from savings in BIK.
'The launch of the new Astra was vital in our decision to switch the contract to Vauxhall.'
Ford will not launch the new Focus in the UK until 2005.
Trinity Mirror has still to decide upon the suppliers for its management fleet of about 300 cars.
Maurice Howkins, Vauxhall and Saab fleet director, said: 'This is further confirmation of how good a car the new Astra is. It has collected plaudits from fleet managers around the country wherever it has been driven and we are now starting to see that praise translated into full order banks for the new car.'