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DEAR CAR TALK: I see that new cars have a small rectangle on the grill of the car. Some are clear and some are solid.

To my eye, it seems to ruin the appearance and pattern of the grills.

I was wondering what purpose they serve.

-- John

DEAR JOHN: They keep you from crashing into a parked UPS truck.

Those are sensors for the safety systems that come on more and more new cars. The newer ones are Lidar sensors that use laser-based radar to detect other objects in the road, be they cars, pedestrians or bicycles.

The Lidar sends out pulses of light, and by measuring how quickly they bounce back, it can tell when there's an object in front of the car and how quickly your car is closing in on it.

For instance, let's say you're traveling on the highway, and you're going 65 mph in traffic. The Lidar will know that the car in front of you is also going 65 mph because your distance from that car will remain the same. Everything is fine.

But, what if the car in front of you suddenly slows down or stops? The Lidar-based system will immediately detect that you're getting closer and closer to that car, and it will go on alert. If it sees that your foot is still on the gas, not the brake, it'll conclude that you haven't noticed the stopped car in front of you, and that's when things get interesting.

Normally, the first thing the system will do is warn you with a light. If you ignore that, it'll add an audible alarm. And if you still can't be pried away from texting your takeout order to the local Chinese restaurant, and the system calculates that you're going to crash into the object in front of you, it will actually apply the brakes to slow the car and either avoid the crash or lessen its severity.

Pretty cool, huh? These systems vary from car to car and come under the generic names "forward collision warning," and "automatic emergency braking." Some work at slow speeds only, while the better ones work at high speeds, too. And some can detect non-car objects auch as pedestrians and bikes.

While they're not perfect, they are, generally speaking, wonderful technological advances that will soon be in all new cars. Plus, they're already saving lives, and sheet metal.

At some point, someone will invent a sensor that can be better camouflaged into the front of the car. But until then, I say, who cares? I'll take an ugly rectangle on my grill if it means saving that grill from getting mangled ... with my own grill right behind it.

DEAR CAR TALK: I bought a used 2008 Ford F-150 about three years ago. It's an excellent vehicle and very trouble-free, except for regular maintenance of course.

The only irritating issue is low fuel economy. I bought a cover for the bed and that improved the mileage, but it still gives me only 16-18 mpg.

Any suggestions for better miles per gallon? Thanks.

-- Frank

DEAR FRANK: Yeah, a Toyota Prius.

If you bought a zebra, you'd expect it to have stripes, right, Frank? Well, you bought a pickup truck, and you should expect it to get mediocre gas mileage. That's baked in.

In fact, 16-18 mpg sounds pretty good to me. The EPA rating for this truck, back in 2008, was 14 mpg city and 19 highway, with an average of 16 mpg. So, you're already exceeding expectations.

If you had come to our shop and said that you used to get better fuel economy, and it had dropped recently, there are some things we would check.

The first would be your reliability as a witness. But if you survived our cross examination, we might start by checking your tire pressure. Low tire pressure is not only dangerous, but because it creates a bigger patch of rubber on the road, it creates more friction and can also result in lower mileage.

We'd also check your thermostat. If your thermostat were stuck halfway open or opening too early, your engine might not be getting all the way up to operating temperature. And an engine running cool will run inefficiently, with lower mileage.

We might check for an obstructed exhaust too. If your engine wasn't breathing properly, that could lead to wasted fuel.

Finally, if it's an old vehicle, we might check the compression, because an engine that's not fully compressing its fuel-air mixture is obviously not getting the most out of each drop of gas.

In your case, I really doubt you've got any problem at all, Frank.

If you really want to see if you can improve your mileage any further, you might want to try overinflating your tires by a few pounds more than the recommended pressure. Just be sure to stay below the tire manufacturer's maximum pressure.

Also, you can make sure your truck is empty when you're not actively hauling anything. Extra weight will decrease mileage. And you can drive slower. The difference in fuel economy between going 75-80 mph versus 55-60 mph is enormous. If it matters that much to you, slow down.

But don't expect any miracles, Frank. You're already at the winning end of the F-150 fuel economy bell curve.

Ray Magliozzi dispenses advice about cars in Car Talk every Saturday. Email him by visiting:

HomeStyle on 11/30/2019

Print Headline: Car Talk

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