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This week we've been looking at how the auto industry is planning to meet ambitious fuel efficiency goals - an average of 55 miles per gallon. That's the fuel economy standard the Obama administration wants to see by 2025. We've looked at hybrids and electric cars. Now NPR's Sonari Glinton looks at the plain old internal combustion engine.

SONARI GLINTON, BYLINE: I wanted to find out where the new technology is being developed to make gas engines more efficient. So I went on a tour of an engine lab with Professor Anna Stefanopoulou. She's the director of the Automotive Research Center at the University of Michigan. I was expecting cams and pistons, but first she shows me computers screens.

ANNA STEFANOPOULOU: Well, it's hard to see since a lot of the work we do is not necessarily only hardware. It's software.

GLINTON: So...

STEFANOPOULOU: If you really need to reach the 50 miles to the gallon goal, and need to do it cost-effectively, you have to do it sometimes through strategy.

GLINTON: Eventually Stefanopoulou and I wound up looking at one of about a dozen engines that they test here.

And how often do you test it, this engine?

STEFANOPOULOU: We test it once a week, sometimes once a day. We don't run durability tests here. We run tests to model the engine and then be able to understand what is going on with running different fuels.

GLINTON: This particular engine can run on a variety of fuels. Stefanopoulou and her students are working to perfect every part and function in the engine. Now you can put computers or even tiny crystals right into the engine that will help it strategize.

STEFANOPOULOU: So putting in a computer it can monitor in real time what is happening inside the cylinder, and communicating this to a mathematical formula, that the formula says: Now I want you to be a little to the left, a little to the right, when it comes to the picking of the pressure.

GLINTON: They don't just work on engines but with how drivers perceive the driving and they do it with psychologists and statisticians. Stephanopoulos and her colleagues say the barriers to getting to 55 miles a gallon aren't scientific.

MARGARET WOOLDRIDGE: When we talk about 55 miles per gallon, we had that technology, criminy, 20 years ago.

GLINTON: Margaret Wooldridge is also a professor at the University of Michigan in the Department of Mechanical Engineering. She says there's a but. And in this case it's the car driver.

WOOLDRIDGE: Like when was the last time you took your hand and actually rolled down a window? But now there's an expectation that every vehicle, even if its entry-level vehicle, will have that kind of creature comfort.

GLINTON: Wooldridge says we expect our cars to heat faster in winter, to cool faster in summer, have seat warmers plus plug in two cell phones, maybe even a DVD player - oh, and a radio - you can't forget the radio.

WOOLDRIDGE: So, you know, I personally owned a vehicle that had over 45 miles per gallon fuel economy when I was in college. And it had manual transmission, it manual windows, it was a great car, lasted forever. It was lightweight, kind of chilly to, you know, heat in the winter and all that good stuff.

GLINTON: Wooldridge says all those extras can reduce the fuel economy by up to 50 percent. She says it's a fat chance people are going to give up plugging in their cell phones or running the air conditioner or cranking NPR.

WOOLDRIDGE: Expecting people to make good choices at a cost premium isn't going to work. So if we're trying to effect positive change, if we're trying to change behaviors, and change emissions and things like that, you're not going to get people to do that unless you can do it cost competitively.

GLINTON: Wooldridge says there are many regular inexpensive gas-powered cars that get more than 40 miles a gallon. The real race is to do that with all kinds cars, from showy luxury cars to economy cars.

WOOLDRIDGE: You need it all. You have to have it all. You're not going to get there exclusively on one engine technology or one power train technology. You have to have a variety of power train technologies. So hybrids have a role to play. They absolutely do. Electric vehicles have a role to play.

GLINTON: Wooldridge says regular gas engines are going to be on the road for quite some time to come. She says the science exists to make cars vastly more fuel efficient. The limits, she says, are cost and our desire to get there.

Sonari Glinton, NPR News.

WERTHEIMER: It's MORNING EDITION from NPR News.

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