Hours before the Stanley Cup play-off at the Capital Centre yesterday, a tanker truck hauling 6,000 gallons of heating oil ruptured on the John Hanson Highway, spreading a two-mile slick that forced traffic going to the Centre onto the Baltimore-Washington Parkway.

The tanker, operated by Andergo Oil of Washington, was turning east onto Hanson Highway from Interstate 295 when the driver, John L. McManus of Baltimore, said he looked into his rear-view mirror and saw oil dripping between the wheels of the trailer. To avoid polluting a nearby creek, McManus said he drove another mile and a half, and pulled off just past the Landover Road exit.

The tanker lost an estimated 2,800 gallons of No. 6 heating oil, which resembles molasses or tar, according to William S. Burgess, chief of the spill response team of the Maryland Water Resources Administration. Rain spread the oil onto the shoulders, and the Maryland Water Resources Administration and Hyattsville fire crews dammed nearby Beaver Dam Creek to prevent its contamination.

State police, who coordinated the cleanup, closed eastbound lanes of Rte. 50 between Kenilworth Avenue and the Ardwick-Ardmore exit from 9:30 a.m. until about 6 p.m. A Hyattsville Fire Department spokesman said the oil presented no fire hazard, and there were no injuries reported.

Crews from the state highway department and workers from Warren Tank Co. of Oxon Hill covered the road with cinders and gravel. The remaining oil was pumped out of the disabled tanker into a nearby ditch and temporary, plastic holding tanks. Vacuum trucks from two Baltimore firms, Clean America and J&L Industries, were used to remove the sticky oil from the ditch and holding tanks.

McManus blamed the leak on potholes. He speculated that bumpy city streets had caused a spring to pop at the base of the left rear wheel and puncture the tank.