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TOUCH-UP WILL DO THE TRICK

Dear Tom and Ray: My wife has the unfortunate habit of side-swiping our house with our '94 Dodge Caravan. The first time she did it, we took it to the body shop to have the dented plastic side piece replaced and various scratches repaired.

Well, she has done it again (twice, actually). My question is, is this body work important to the car's health? Or can I just use some touch-up paint and forget about it?
-- David

Ray: I would absolutely follow the touch-up-paint-and-forget-about-it route, David. Unless one of your kids is about to go into the auto-body profession.

Tom: The damage she's doing sounds minor and purely cosmetic. She's not bending the frame or causing any structural damage. If it's just the plastic, you can forget about it completely. If she scrapes metal, all you have to do is sand it down a little bit, apply some primer, and then cover it with a coat or two of touch-up paint. It won't look perfect, but it should keep it from rusting.

Ray: And my guess is that she'll probably feel better about it when it's just touched up like that. It probably makes her tense to know it's just been repainted for hundreds of bucks and she'd better be careful not to . . . (crunch) . . . oops!

Tom: Someday, after she finally rounds off that corner of your house, you may decide to have the thing smoothed out and repainted.

Drip and a headache

Dear Tom and Ray: I own a 1993 Subaru Legacy Wagon. It's the 25th Silver Anniversary L Plus Sports Wagon Edition. That means I have a sports suspension, fancy wheels, turbo, leather steering wheel and leaking electric sunroof. When it rains, the sunroof leaks on my head, just like the old B.J. Thomas song. No one except the dealer will even look at this for me. The dealer thinks the silicone rubber seal is in need of replacement (the drains are clear). Even though silicone costs $4 a tube, the cost estimate is for eight hours of work at $60 per hour. They say it's so expensive because they have to remove the headliner, sunroof and other items.

I cannot believe this thing is leaking after only four years, and can't believe how much it costs to fix. Do I have any alternatives? Should I attempt this on my own? Or should I just do it and get on with my life?
-- Ted
Ray: You should absolutely, definitely not attempt this repair yourself. You could more easily fix the leak in the Mir space station. The dealer is right about what's involved with this job. This is a complete pain in the butt.

Tom: But I think you're right to be disappointed that the sunroof is leaking after only four years. And if it were me, I'd complain to Subaru and see if they'll contribute to the repair (the customer service number is 800-SUBARU3). As always, be polite and tell them how much you like the car, and that you're surprised that the sunroof didn't last longer.

Ray: And if you get nowhere with Subaru, then you have two choices. You can either throw in the towel (so to speak) and get it fixed, or you can do what my brother would do: Go the duct-tape route.

Gates up

Dear Tom and Ray: I read your recent article in which a reader (also named Kathy) asked whether a pickup truck gets better gas mileage with the tailgate up or down. You guys said "down."

My husband and I made a very large bet about the very same issue. I work for GM as an engineering intern and had a chance a couple of weeks ago to tour the design facilities in Detroit. When I got to the wind-tunnel building, I asked the engineers this same question. They laughed and demonstrated that trucks are designed so the airflow creates the least amount of drag when it flows off the roof and past the tailgate in the upright position. They said that leaving the tailgate down would actually decrease a truck's fuel mileage. So guess who won the bet, guys?
-- Kathy
Ray: We know who won the bet, Kathy, because we received letters about this from engineers scattered throughout the automotive industry.

Tom: Here's one that offers a more technical explanation for you (still) non-believers.

Dear Tom and Ray: I'm an aerodynamics engineer. When I was in the Air Force a few years back, I worked with folks from the Lockheed low-speed wind tunnel. In the 1970s, aircraft production went into a slump, and Lockheed started looking for other customers for its wind-tunnel services. Prime candidates were the auto makers, and Lockheed was successful in convincing Ford, among others, that the wind tunnel would help them reduce drag and wind noise on their vehicles. Needless to say, in the past 15 to 20 years, Lockheed has learned a lot about car and truck aerodynamics.

Anyway, they actually per-formed drag tests on pickups with the tailgate both up and down, and found that drag was actually lower with the tailgate closed. This ran counter to their intuition (and yours). The reason is that a closed tailgate sets up a large "bubble" of stagnant air that slowly circulates around the bed of the truck (we aero types call this a "separated bubble"). When air approaches the truck, it "sees" the bubble as part of the truck. So to the air, the truck looks like it has a nice, flat covering over the bed, and the air doesn't "slam" into the vertical tailgate.

If the tailgate is open, or replaced by one of those "air gate" nets, however, that nice, separate bubble in the truck bed does not form (it "bursts"). Then the air approaching the truck "sees" a truck with a flat bed on the back of a tall cab. This is a very non-aerodynamic shape with a very large drag.

So, believe it or not, it's best for gas mileage to keep the tailgate closed.

-- Ed Fitzgerald,
Research Assistant,
Department of Aero/
Mechanical Engineering,
University of Notre Dame
Tom: Sounds pretty convincing, Ed. Thanks. We also heard from none other than Bob Stempel, the former GM president, who wrote us to say that aerodynamically it doesn't make that much difference. But, he says, a pickup truck is structurally much safer with the tailgate up.

Write to Car Talk in care of The Buffalo News, P.O. Box 100, Buffalo, N.Y. 14240. Tom and Ray can't answer your letter personally but will run the best letters in the column. Their radio show airs at 7 and 10 a.m. Saturday on WBFO (88.7).

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