overheating and 160 thermo

[stng87]

I have had recent overheating probs and I am wondering if it could possibly be fault of the 160 degree thermostat that i am currently utilizing. The engine usally always runs at 160 until it started to slowly slowly crawl up closer to 200 and beyond if i let it. I changed it and it seemed to be better for a month and now its doing it again. Even if im cruising at 70 during the day itll run at 180(never 160 anymore) for a long time then clowly creep up again. But night driving is fine, i seem to sit at 160 after the cali sun goes down.
What i suspect is that the 160 degree thermos all allow too much coolant flow so the coolant never has enough time to be cooled. Could this be a possibility. Seems to make sence to me.