Your car is not operating at 20% efficiency of theoretical limits if you take the whole energy pipeline into account. You know... fusion, sunlight, plankton, oil, refining, combustion, mechanical energy. On the other hand speed-of-light to actual ping times is an end-to-end efficiency calculation. Plankton in particular is terrible at converting energy.

sun -> mj-PV -> battery -> electric motors run circles around those.