The next time you go to remove the oil lines connected to the oil thermostat, you may find that half the threads have come off with the oil line. Now instead of replacing a $300.00 oil thermostat, you can easily screw on this coupler to the un-damaged portion of the threads still remaining on the thermostat. Once the coupler is attached, the oil line (with clean threads) is now re-attached to the new coupler as if it were the original part of the thermostat.