Brazil's state-owned oil and gas giant Petrobras on Monday kicked off tests to verify the performance of vehicles powered by a mixture of diesel fuel and bio-diesel.

By 2013, all of Brazil's diesel will have to include 5 percent of bio-diesel.

In a partnership with U.S. automaker Ford, the Brazilian company will have three diesel-powered cars run 100,000 km to check the fuel's effect on their performance.

One of the vehicles will use diesel mixed with bio-diesel made from soybeans, and another one will use a mixture of diesel and bio-diesel made from castor beans. The third car will use ordinary diesel fuel.

Bio-diesel made from soy and castor beans are being produced in Petrobras' pilot plants in northeastern Brazil.

Petrobras currently supplies 4,000 petrol stations throughout the country with "B2" fuel, which is 2 percent bio-diesel. The distribution of fuel with such a percentage of bio-diesel will be required in 2008.