Variables in my Service/IntentService are reset on every start

Question

I declared a service, that shall act as a queue. Therefore I have a variable that tells the service it's the first start and another one that stores a value.

The code looks like this:

public class TTSQueue extends Service {

private Integer lastvol = 0;
private Boolean isFirstStart = true;

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    Bundle b = intent.getExtras();
    Integer vol = b.getInt(TTS.PARAM_LAST_VOL, 0);
    if (vol > lastvol) {
        lastvol = vol;
    }
    if (isFirstStart) {
        isFirstStart = false;
        startAnotherService();
    } else {
        waitForAnEventAndThen_startAnotherService();
    }

}

Okay, the problem is, this Service is started from a receiver. And everytime it is started, both lastvol and isFirstStart are reset. I thought, if the Service is already created and then started with an Intent, it would only call onStartCommand() again and not reset everything.

I also tried only declaring the variables and setting them to the default value in onCreate(), but that had the same effect. Also I tried replacing the Service with an IntentService, but that doesn't help either, same problem.

I would like to avoid using SharedPreferences, as I don't think it is necessarily needed in this case. (And I don't want to waste the user's Write Cycles).

Am I missing something? I guess it is not because of the private declaration, is it?