He suffered a heart attack at his Redmond, Washington home on January 26, 1981, and died at the age of 42. He is buried in an unmarked grave at Sunset Hills Memorial Park, Bellevue, Washington (Gethsemane Section, Grave 85).
In a May 2007 article titled "Baseball, Partying, and Alcohol Abuse," Oyler's former Detroit roommate, Denny McLain claimed that Oyler was "an alcoholic" who "died prematurely."[13] One of the authoritative histories of the team also reports that many of the 1968 Tigers drank "a lot," that Oyler was "later in AA" and that "alcohol may have adversely affected (Oyler's) career." (Patrick Harrigan, "The Detroit Tigers: Club and Community 1945-1995" (Univ. Toronto Press 1997), p. 145.)
That's from Wikipedia, which as far as I now is all verified information!