coolant temp. sensor, water temp sensor Options

[timdog1720]

On my Caldina ST-215 engine, I have on there the original water temperature sensor which gives me a good signal out (meaning the gauge on the cluster says its just below middle when warmed up, NORMAL) My problem with my car is that it burns incredible amounts of gas. one of the symptoms of that is a bad water temp sensor many say.

So I go ahead and three times I changed the sensor to one i purchased online, auto-zone, and pep-boys. Every time I place the new one in my gauge starts off cold then spikes all the up to HOT and seems to past it lol. I checked the sensor for the ST-215 is: DENSO 89422‑16010 which is the same used in North American built cars in:

06/2003-07/2005 TOYOTA ECHO NCP13 84-04: ELECTRONIC FUEL INJECTION SYSTEM
04/2003-11/2006 SCION XB NCP31 84-04: ELECTRONIC FUEL INJECTION SYSTEM
01/2001-10/2005 TOYOTA YARIS SCP1*, NLP10 84-04: ELECTRONIC FUEL INJECTION SYSTEM
04/2003-11/2006 SCION XA NCP61 84-04: ELECTRONIC FUEL INJECTION SYSTEM
09/1994-06/1999 TOYOTA TERCEL EL53 84-04: ELECTRONIC FUEL INJECTION SYSTEM
08/1999-10/2005 TOYOTA ECHO NCP12 84-04: ELECTRONIC FUEL INJECTION SYSTEM
08/1995-06/1999 TOYOTA PASEO EL54 84-04: ELECTRONIC FUEL INJECTION SYSTEM
08/1997-12/2001 TOYOTA COROLLA ZZE110 84-04: ELECTRONIC FUEL INJECTION SYSTEM
07/2001-01/2006 TOYOTA CAMRY ACV30,MCV3* 84-04: ELECTRONIC FUEL INJECTION SYSTEM
07/2001-12/2005 TOYOTA CAMRY ACV30,MCV3* 84-04: ELECTRONIC FUEL INJECTION SYSTEM
06/1998-11/2002 TOYOTA SOLARA ACV20,MCV20,SXV20 84-04: ELECTRONIC FUEL INJECTION SYSTEM

Now every time I place the original sensor back the gauge stays in the normal range. What does this mean? I'm replacing it with the correct part but all the other ones tell me I'm running hot at idle.

PS: No the engine doesn't seem hot. It seems as if it is as hot as any other engine when touching it, and also when I put the replacement sensor in and rev the engine, it goes past hot but if you let it idle the needle goes to about 80 -90% up the gauge.

Thanks Guys always for your help