STERLING HEIGHTS, MI – General Motors Corp.’s Saturn division used dent-resistant thermoplastic body panels as a selling point when the import-fighting brand launched in 1990.

But in a bid to revitalize Saturn with more dramatic styling and tighter body-panel gaps – as well as to commonize vehicle architectures globally – GM opted for steel when it launched the new Saturn Sky roadster, Aura sedan and Outlook cross/utility vehicle in 2006 and Vue CUV in 2007.

Plastic is a thing of the past at Saturn. Or is it?

With some auto makers reporting sheet steel prices up about 30% this year, GM insiders aren’t ruling out a switch back to plastic panels in certain, limited applications. But huge hurdles remain.

“If ever there was a time to get back into plastic, now is the time,” Maureen Midgley, executive director of GM’s global paint and polymers center, says in a panel discussion at this week’s SPE Automotive TPO Global Conference here.

After the session, Midgley says there is no concerted migration back to plastic body panels within GM, and designers are not pushing in that direction. But she says GM will consider other exterior applications for plastics, and that designers within GM hold the key.

“Right now, they design cars that can be made out of steel because that’s their medium,” she tells Ward’s. But Midgley says those same designers also are open to plastics if they achieve a key objective that steel cannot. “Our designers are creative,” she says. “I’m talking specifically about exterior now. That’s what was unique about Saturn, the exterior.”

Exterior plastics already are used extensively in front and rear fascias and for rocker panels, and Midgley says plastic body panels could be considered for small, niche vehicles. The Chevy Volt extended-range electric vehicle, set to arrive in 2010, will use steel body panels and plastic front and rear fascias.

“There are a lot of things that plastics are good at – for stone impingement and bumper impact,” she says.

Midgley is intimately familiar with Saturn’s foray into plastic body panels. She started as an engineering manager and went on to run the paint shop and polymer and stamping operations in Spring Hill, TN.

She remains “pained” by the large number of reject body panels that ended up in landfills, and she recalls extreme challenges associated with tooling up for the panels and achieving proper fits and surface flushness.

“It was expensive to get into it, expensive to get out of it, and it would take an awful lot to get back into it,” she says at the conference.

Although steel prices have spiked dramatically, resins used to manufacture plastics haven’t been much better, given the unstable petroleum market. Crude oil prices have plummeted since the July record of $147.27 per barrel. On Oct. 9, Bloomberg reported oil trading for $88 a barrel, the lowest price since December 2007.

Asked if GM plans to step up its applications of thermoplastic olefin parts, Midgley says TPO certainly makes sense for recyclability and weight reduction, but surface quality and the “waviness” of body panels remain as severe hurdles for auto makers.

“Customer perception plays against plastic,” she says. “Customers have become more sophisticated, and there are few markets in the world that will accept less just so we can cut weight and improve recyclability.

Plastics consultant Robert Eller says TPO automotive applications are growing at the rate of about 10% annually, with interiors representing the latest area of expansion.

tmurphy@wardsauto.com