Column not found when creating list item with Javascript

I am making a SharePoint app with javascript.

I am trying to add a list item to a list I have defined in Visual Studio. I have done this just by adding a list in the solution explorer, and I made some custom columns in the graphical view. This is actually where I suspect my error could be located. Is this how I define my columns? My code looks like this

var oListItem = null;
function createListItem() {
    var oList = clientContext.get_web().get_lists().getByTitle('List');
    clientContext.load(oList);
    var itemCreateInfo = new SP.ListItemCreationInformation();
    oListItem = oList.addItem(itemCreateInfo);
    clientContext.load(oList.get_fields());
    oListItem.set_item('Car', 'My New Item');
    oListItem.update();


    clientContext.load(oListItem);
    clientContext.executeQueryAsync(
        Function.createDelegate(this, onQuerySucceeded),
        Function.createDelegate(this, onQueryFailed)
    );
}

function onQuerySucceeded() {
    alert('Item created: ' + oListItem.get_id());
}

function onQueryFailed(sender, args) {
    alert('Request failed. ' + args.get_message() +
        '\n' + args.get_stackTrace());
}

I am able to print out the list and the fields, but I am not able to add the item like this. I get an error telling me:

Request failed. Column 'Car' does not exist. It may have been deleted by another user.

What can I do to be able to add some items to my list? Do I have to define my list otherwise?