The United Steelworkers union and oil companies have reached a tentative deal to end the largest U.S. refinery strike in 35 years, the labor group and people familiar with the negotiations said on Thursday. The new agreement for about 30,000 workers would last four years, a year longer than previous agreements. The deal, which still needs to be ratified, may not end strikes right away at all refineries that have suffered walkouts as local union chapters could still need to work out pending issues. “We salute the solidarity exhibited by our membership,” said USW International President Leo Gerard. “There was no way we would have won vast improvements in safety and staffing without it.”