Class method returning 0

I am scratching my head here...

Problem: I am doing a basic method to calculate two object fields and return a value. For some reason it is returning a null value. I know I am overlooking something incredibly simple but it is kicking my butt.

Code:

public class Tools {

    // Instance variables
    private String type;
    private int age;
    private int eol;
    private Double lifeLeft;

    // Constructor
  public Tools(String type, int age, int eol) {
    this.type = type;
    this.age = age;
    this.eol = eol;
  }

  public String toString() {
    return type + " has reached " + lifeLeft() + "% of its life expectancy.";
  }

  public Double lifeLeft() {
    lifeLeft = (double)((this.age / this.eol) * 100);
    return lifeLeft;
  }
}

I am simply attempting to calculate lifeLeft = age/eol * 100 to get a percentage. I have tracked the issue back to my lifeLeft() method. For some reason it is not getting the age and eol of the object. I have done some System.out.println(age, eol) etc to test and the variable values reflect 0.

Sidenote: I am calling super.toString() from a subclass object but I don't think that matters here.

Subclass for reference in case it does.

public class Wrench extends Tools {

  // Instance variables
  private Double capacity;

  // Constructor
  public Wrench(String type, int age, int eol, Double capacity) {
    super(type, age, eol);
    this.capacity = capacity;
  }

  public String toString() {
    return "Your " + capacity + "\" " + super.toString();
  }
}