Bill Elliott held off Harry Gant yesterday for his first NASCAR victory of the year and his third straight Miller American 400 title at Michigan International Speedway in Brooklyn, Mich.

Elliott, in his Melling-Coors Thunderbird, refused to let Gant pass him on the final lap and built a lead of five car lengths. Geoff Bodine finished third, 20 car lengths back. Buddy Baker was fourth and Darrell Waltrip fifth.

Elliott became the 11th driver to win a NASCAR race this year. His average speed was 138.55 mph.

Elliott stalked Gant for five laps before moving ahead for good on the 195th lap.

Richard Petty, making his record 1,000th NASCAR start, never was a factor in the race.

Pole-sitter Tim Richmond led the first seven laps. He was fourth through 130 laps but finished in the back of the field . . .

Mario Andretti caught his son Michael, who had run out of fuel, at the finish line for the closest victory in Indy-car history in the Portland (Ore.) 200.

Michael Andretti appeared to have his third victory in five races this season wrapped up as he completed the final lap in the 104-lap race.

But he ran out of fuel and slowed down on the final straightaway, which allowed his father to edge him at the finish.

The margin of victory was .07 seconds, breaking the old mark of .14 seconds, set when Mario Andretti won the Michigan 500 in 1984.

"I just ran out of gas," Michael Andretti said. "I started running out of gas the last two laps. Happy Father's Day, Dad."

Al Unser Jr. finished a close third, just behind the Andrettis . . .

Nigel Mansell drove to an easy victory in the Canadian Grand Prix in Montreal, the second straight Formula One triumph for the Williams-Honda driver.

The Englishman, who made a daring pass on Keke Rosberg of Finland to retake the lead early in the race, drove away from the field after a scheduled pit stop for a tire change just before the halfway point. Mansell's time was 1 hour 42 minutes 26.415 seconds, and he averaged 110.75 mph.

Alain Prost's second-place finish moved him past Brazil's Ayrton Senna into the world championship lead with 29 points after six of 16 events.