In a big garage-size laboratory in Ford Motor Co.’s sprawling research complex in Dearborn, Mahendra Dassanayake stands beneath a planetarium-like dome that can replicate the sun.

It can surround new cars and trucks with an eye-squinting 5,000 watts of light. Or mimic the fading light of dusk. Or make the room turn black, like a backwoods street where there are no city lights or ambient light from the stars or moon.

In this visual performance evaluation lab — dreamed up by Dassanayake and put into use a little over a year ago — Ford can evaluate new interior and exterior lights in virtually every lighting condition mother nature and the manmade world has to offer.

But the research isn’t just about offering better, cooler lights. Ultimately, it’s about improving fuel economy with more efficient lights, such as those that use light-emitting diode (LED) bulbs.

About 5% of fuel consumption goes directly to power a vehicle’s interior and exterior lights, said Dassanayake, a senior staff technology specialist at Ford. So, more efficient lighting systems, which offer good luminosity with less power, could ultimately save consumers at the gas pump.

Lately, Dassanayake’s lab has focused on the benefits and challenges of LED lights over other forms of bulbs, such as incandescent, halogen or fluorescent versions that generally use a filament that must be heated and gas to create a visible spectrum.

LEDs don’t have a filament that can burn out. Rather, they are illuminated solely by the movement of electrons in a semiconductor material, called a diode, which is a small, long-lasting chip.

Bulbs with light-emitting diodes are about twice as efficient as the other light forms, and usually 10 times more expensive. But Dassanayake said that if the lighting systems of all future vehicles were LED, consumers could save as much as a gallon of gas per week.

“We are not doing LEDs for the sake of LEDs,” he said.