[kedikedi]

You can but it isn’t efficient. You lose (V_in - V_out)*I_led Watts to heat if you use a linear regulator.

You might ask why not connect them in series and get the voltage difference as small as possible. But the “forward voltages” of LEDs are highly temperature dependent and car battery voltage is (somewhat) engine rpm dependent (might swing between 12 and 13.8V between no rpm and some rpm. It’s kept flat at 13.8V)