I came across a question- how much voltage it takes to kill 10W 12V LED. So i took my 50V power supply and tested the LED. I bought these LEDs at ebay for very cheap. One segment in LED started glowing at about 5.5V, I kept rising the voltage. I came to 15V and current draw was about 0.7-1A. I kept rising voltage slowly. At about 22V LED started to lose it's brightness permanently. I got to 50V and LED was glowing just a bit and drawing almost no current. I couldn't go to higher voltages because my power supply can only deliver 50V. And LED kept glowing at 50V and not losing brightness. As i turned off power i seen dark spots on LED where separate LEDs are. Photo is below:
Step 1: Dark Spots on LED
Conclusion is that you can connect 12V LED in car where is 14V and nothing will happen to LED.