1993 Geo Prizm Thermostat Range?

My wife drives a 1993 Geo Prizm LSI 1.6 litre automatic, which is actually a re-branded Toyota Corolla. The temp gauge never creeps above the cold mark until the engine has been driven during the day for a while. I was told that the thermostat is probably stuck open, so I want to replace it. But when I checked out O’Reilly Auto for pricing, it gave me three options: 170-179 degree, 180-189 degree, and 190-199 degree. So which one should I get? Is this determined by our local weather? We live in NW Washington where summer is only about a month long, and never gets above 85. Our winters are around freezing with snow and ice. And, as you might expect, we get a lot of rain during the year. Any suggestions?

Either the 180 or the 190 should do the job…Most modern cars come with a 195, which will provide the most heat in the winter…

It is very important to get the OEM temp thermostat. For this car, it is the 180 deg. thermostat according to my source. That parts counter guy should know which one is OEM. His computer should flag the OEM temp for the given car. Getting a different thermostat may confuse the computer and cause problems like reduced fuel economy, carbon build-up, and long-term damage to the catalytic converter.

A lot of cars can use the same size thermostat, and require different temp ranges, which is why so many are available.

Trust me I have owned many Prizms and Corollas. Get a thermostat from Toyota. Every time I did the after market ones I ended up with the problem you have. Put a Toyota one in problem always solved.

I guarantee you Toyota does NOT make the thermostat. There are aftermarket parts and then there are aftermarket parts. I’ve NEVER EVER had a problem with any aftermarket thermostat (or any after market part for that matter) when bought at a reputable parts store. I’ve had problems with parts bought from ADAP and Autozone and Pepboys though.

I’ve never seen an aftermarket thermostat that looks as well made as the thermostats sold by the Honda and Toyota dealers.
I don’t know who actually makes them and I don’t care.

I agree with circuit. I just bought one from Toyota for my 91 Prizm GSI because the new after market ( stant ) was taking forever to warm the car. The Toyota replacement was in a Toyota box. Looking at them side by side the Toyota stat was so much better made than the stant. Installed works perfect.