Normally in moderate conditions of around 70F oil temps would stay right at 185F unless I started getting on the throttle. Eventually outside temps got low enough my oil struggled to reach 145F and wouldn’t go above 160, so I blocked off the cooler until I had the time to install the mishimoto 200F thermostat. However, after installing it during my last oil change I’m not seeing any difference even with ambient temps being in the 70’s. Oil temps still hover around 185.

Conditions haven’t been cold enough to see if it will make a difference, but I was expecting to see higher oil temps. Has anyone else gotten different results after doing this swap?

 

My oil temps hover around 180-190 as well. I would think this is an ideal temperature? When it goes above 200 the engine doesn't feel too crisp

 

A thermostat bypass valve used in oil coolers will still allow about 10% of flow to loop through the cooler in order to eliminate cold shock and air pockets, at about 20f below the rated open temp in your case now 200f it will begin to open further, for example it will start to open more at 180f and at 190f it should be about 55% open.

In your case when cold out regardless of 185f thermostat or 200f thermostat your temps are well bellow the starting open temp of both of them, so switching from one to the other will not resolve or have any impact to your cold warm up situation.

switching from 185f to 200f will only impact warm up, speeding it up only once it is already at 165f(starting open temp of 185f thermostat) but the flow allowed to go to the cooler at 185f (even with 200f therm) may still be great enough to keep the oil temps from exceeding 185f in normal driving there may just not be enough heat being introduced into the system to get it to go higher under those conditions.

this is why I use fans and often intentionally limit incoming airflow to the coolers, so it will warm up at a similar rate to using a block off plate but then once warm the fans will kick on and keep it cool, maintaining ideal operating temps.