Complex sentence: By leading the final 18 laps, Unser, Sr. tied the all-time record for most laps led in Indy 500 competition, and, at 47 years of age, also became the oldest winner of the 500.
Split into simpler sentences: By leading the final 18 laps, Unser, Sr. tied the all-time record for most laps led in Indy 500 competition. At 47 years of age, Unser became the oldest winner of the 500.