what temp thermostat is best

[1992/SC400]

I want to change my thermostat but at NAPA they had a 170 and a 180. I would like to go with the one that is best for my 1UZ and I have heard that a cooler one gives more HP but I just have the stock ecu and do not want to screw with that.

Thanks

 

[Nick M]

Stock is best, and best quality. The reason stock is best, is yes, the computer. An engine runs better when it is warm, and the car is programmed that way. Some cars can gain a small hp advantage by being slightly richer. Most dont though. If anything, with Toyota a little leaner is a little meaner.

 

[1992/SC400]

What is stock 170 or 180? I think it is 180 but the napa guy said it was 170.

Thanks

 

[Toysrme]

IDK on a 1uz-fe.
Toyota almost exclusively uses a stock 190*F thermostat that is fully open by 212*F. Hotter running engines are supplied with a 180*F. While the TRD units are mostly 160*F, a few are 170*F.

Off-hand I can't name a stock Toyota engine that comes with a sub 180*F thermostat.

 

[SCV8]

Even more of a reason to stay with the stock unit is that the engine control computer may remain in cold-mode, without many of the features that help with efficiency, smooth running, etc., also known as open loop.
This is more of a default mode, and is what the computer will also turn to when some the sensors have gone bad.