[wagonman76]

Well what I perceived as "warm" was slightly warmer than 20F. I tested them outside where I could see how far they would shine.

Even in the summer the chances of seeing 90F in Michigan is little to none. I could try running a few in a destructive test, leaving them on all day next to the woodstove and as long as they still work the amps should be ok.

One thing I like about using 3 in series is the resistor value is larger. It would handle voltage variations in the car without much change in LED amps. Using 4 in series means a smaller resistor and though they worked nice with my steady power supply, a variation in car voltage could either make them not work or could fry them.