window.onload Javascript, with functions that receives parameter?

Question

I have this function:

<script type="text/javascript">
    var car = document.getElementById("Carros").value;
    window.onload = ChangeValue(car);

    function ChangeValue(str)
    {   
       ....
    }   

See that ChangeValue(str) receives a parameter, how may I make it start in the pageLoad?
using javascript ! The parameter I pass is a <select id="" onChange="ChangeValue(this.value)">

Answer 1

window.onload = function () {
    var car = document.getElementById("Carros").value;
    ChangeValue(car);
}