It's easy to talk about automotive interior lighting in concept. Designers want lighting “solutions” that create “ambience” by “bathing” the cabin in light — not the entire cabin, just those spots that need it. The more expensive the car, the more intense the need for “mood lighting.”

And it's no longer adequate to stick a single light on the headliner and expect it to meet the illumination needs of all occupants. The industry has concepts for lighting everything these days — grab handles, locks, switches, cupholders, seatbelt buckles, mirrors, side sills and storage bins. Some of these already are in production.

Federal-Mogul Corp. has a prototype minivan showing off a lot of these lighting concepts — even a sliding dimmer function to make the light as bright or as soft as needed. Add a little candlelight and a Barry White soundtrack and the romantic possibilities could be endless. The company is preparing the dimmer for production in the coming year.

With vehicles getting bigger, one light doesn't cut it. When Ford Motor Co. redoes its huge Excursion sport/utility vehicle, perhaps it should talk to Boeing engineers about those nifty overhead swivel lights for every occupant. Now that would be mood-lighting.

But all these glorious lighting options cost money. With vehicle sales softening and cost cuts intensifying, the environment for such non-essential technology is far from ideal.

Some interior lighting features already are being designed out of new vehicles. Take, for instance, the illuminated ring around the ignition to help drivers who fumble with their keys at night. It had become standard on many moderately priced vehicles.

Chicago Miniature Lamp (CML) of Hackensack, NJ, used to supply 1 million ignition lights a year until warranty issues cropped up. The shock and vibration of everyday driving and the constant rotation can be tough on a small incandescent lamp. Today, the company supplies only a few hundred thousand of the units, says CML President Paul Flynn.

“They designed it out, and they're waiting for an LED source and a new design to replace it,” Mr. Flynn says of automakers. “It's something our engineers are working on right now.”

LED is short for light-emitting diode, a tiny, extremely robust light source that many suppliers see as the inevitable replacement for the long-entrenched incandescent lamp. LEDs are used most often for backlighting, as on a cellular phone. The most common use in automotive is the center high-mounted stop light (CHMSL).

An LED is impervious to shock and vibration, and it's good for 100,000 hours of light, compared to 10,000 hours of light from an incandescent lamp. The auto industry's migration toward a 42-volt electrical architecture also should foster the growth of LED in automotive uses.

In North America, LEDs currently make up about 10% to 15% of automotive interior lighting content, with the rest being predominantly incandescent. That figure should jump to as high as 40% in five years and to 75% within 10 years, Mr. Flynn projects.

A year ago, mirror producer Gentex Corp. announced it had a new LED that is 10 times brighter than conventional LEDs. Now it has a powerful partner to market that technology: interiors megasupplier Johnson Controls Inc. JCI packaged the new LEDs on a Ford Expedition concept at the Convergence electronics show in October.

CML, which claims market leadership for instrument panel lighting, is banking on the future of LEDs in the auto industry. In June, the company will open a new plant in Barrie, Ontario, north of Toronto, to produce surface-mount LEDs, with automotive being a key target. The production process is highly automated, and the finished circuit board can be 50% to 75% smaller than a conventionally produced LED.

Besides space savings, the technology produces dramatic cost savings for the customer. It's a good thing because LEDs come with a cost premium. A white LED costs about 70 cents, compared to 10 cents for an incandescent lamp, Mr. Flynn says.

But the auto industry is discovering that a little more money spent up front for more robust LEDs can eliminate warranty claims down the road.

It all comes back to cost, which cannot be underestimated. “We had a project with an LED in a seatbelt buckle to let you find it easier,” Mr. Flynn says. “Ultimately, it was taken out because of cost.”