The image below shows what could be a car LED lamp directly replaceable over the existing holder.
It shows a decent looking arrangement of flat, tiny SMD LEds in a circular pattern for enabling optimal distribution of light via the enclosed hind reflector.
The LED used here are the 3020 SMD LEDs, these tiny light emitting diodes are identical to the ordinary 5mm LEDs with their specs, however if we compare their light intensities, the witnessed difference appears to be huge, where the 3020 easily wins by an outstanding margin, that's why these LEDs are much preferred in place of the ordinary 5mm LEds nowadays.
The technical specifications of the 3020 LEDs are:
Forward voltage: 3 to 3.2V
Forward current: 30mA optimal
Luminous Efficiency: 100-110lm/w