Just received my oil thermostat's and was thinking that when I held it in my hand I would see how it works. Not the case. The illustration online is pretty much how it looks in person. I don't understand (F-2, big surprise I know) how the path of least resistance is not straight through this thermostat whether the oil is cold or hot? Instead, it says that the oil will make 2 - 90 degree turns for approx. 90% of the oil flow during warm up and then go straight through after it warms up enough to close the thermostat then the flow is straight through. I'm not sure what kind of magic is going on here so I thought I would ask you guys. Just to make sure I'm installing correctly, I plan on plumbing from the engine, to the filter block, to this thermostat (from source) from this thermostat (to source) to the engine. The other 2 of course are the external cooler. Thanks for your help.

Path of least resistance mean just that. When the oil is cold its thicker....so its harder for the engines oil pump to push it through the lines....if the bypass is open, the oil will take that bypass route as its a shorter route...it still does move a little bit of oil through the coolers no matter what. Then when the oil heats up the bypass will close off and 100% of the oil gets pushed through the coolers. Very simple design....and its nice because if the bypass was to ever fail it wont completely block off the oil flow.

Wally, I'm holding the thermostat and looking straight through it. How is that not the path of least resistance? Still don't understand how it makes a hard turn twice over straight through. Again, no surprise that I don't get it. I'm sure it works fine. Thanks for your comment.

the cooler is the higher resistance so when open it is easier to make the turn and go back vs thru the tubes of the cooler.

you have to think of it as the lines are full of cold oil the bypass opens and returning most of the oil to where it came from then oil heats up and the bypass closes with free flow straight through

Now I get it. I didn't know the cooler was that restrictive. Thanks guys.

It's not that the cooler is so restrictive. It's the cold oil that's in it that doesn't flow so easily. So it takes the easiest path back until the oil is warmed up and can flow thru the cooler easily.