Can anyone help , We have a 2007 2.8CRD Chrysler voyager - 65k miles on the clock - Over the last month the diesel usage has shot up - Average of 15-17 MPG around town. No obvious leaks or issues with the drive and no errors of fault codes. Can anyone suggest anything I can change or check that might cause this ? I thought maybe O2 sensor but apparently this model does not have one or am i wrong ? HELP Karl