The supermarket said it was "urgently investigating" problems encountered by at least 20 customers at its store at Branksome, Poole.
Customers have complained of damage running into thousands of pounds being done to their vehicles.
Tesco said a first round of tests on fuel sold in Poole had been inconclusive.
The supermarket said more samples had been taken for testing and told customers to continue to take receipts to the store where fuel was bought.
Read more: http://www.bbc.com/news/uk-england-dorset-29306434
Is there water in your diesel fuel? Find out in minutes, using Fleet Fuel Testing’s Water and Visual Clarity test for diesel fuels. The tests are cheap, easy to use, and provide Pass/Fail results in minutes!