Run a 180 deg stat, no reason for anything else... The temp has to climb to what ever the stat is rated for or above before the stat opens. So if you are running a 195 figure the temp will reach 200 before the liquid can flow through the block and core and your cooling system does it's job. Then it's going to cool down some and if it drops below 195 the stat will close and the cycle begins all over again. Your guage may not be calibrated but it's registering the heat rise and drop so that's a good thing. Some stats open slower and the temp will go up a bit more. With a 180 you'll see a bit less movement on the gauge. The 165 stat probably would never close once it opened. It would only be doing half it's job that way...