Dear Car Talk: There are times when I feel like my back-up camera would give me a better view of what’s behind me than the rearview mirror. I’m not talking about when I back up or park. I’m talking about when I’m driving down the road or the highway.

It would be handy to turn the camera on when not in reverse. Any thoughts if this is a good idea and why it’s not an option? — Sam

Yes, it is a good idea, Sam. And I know both General Motors and Toyota happen to agree with you.

There may be other makes that offer it by now, too, but we’ve seen it regularly on GM and Toyota products that we test drive. Essentially, there’s a switch you can flip on the rearview mirror, that changes it from a mirror to a video screen, showing a feed from a rear camera.

I don’t know if it’s literally the same camera that’s employed for backing up and parking, or they use another one that’s better placed for this purpose. But once you flip that switch, you have a nice, clear, unobstructed view of what’s going on behind you. It’s a revelation.

Your view isn’t blocked by the rear headrests, by the D-pillars, by the size of the rear window, or by your great aunt Regina’s beehive.

In addition, cameras and screens seem to get better every year. So, in the cars we’ve driven recently with video rearview cameras, you get a very bright, clear view of everything that’s happening behind your car.

It was clear to me instantly that it’s a vast improvement over a rearview mirror — which has been around since the Model T. Rearview mirror technology has also become less and less useful over the years as rear windows have gotten smaller, and D-pillars — the structural supports around the rear window on SUVs and wagons — have gotten thicker and more stylish.

There’s only one downside I discovered, Sam. When you’re using your rearview mirror for a video feed, you can’t use it to check and see if you have a piece of spinach in your teeth.

Dear Car Talk: I read your column about the guy who wanted to warm up his car in the garage with the garage door open. You recommended against it.

A few years ago, one of our tenants called from our rental house to tell us that they had called 911, because their carbon monoxide (CO) detector had gone off in the house.

By the time I got there, there were trucks from the utility company and fire department, plus an ambulance already crammed into the tiny street. And there were enough flashing lights to open a disco.

They detected no CO, but had shut off the gas line to the house, and we had to have a plumber come to check the water heater and have the furnace serviced before they would turn the gas back on.

When all that was done, the utility company installed a sensor in the garage for 24 hours to monitor the area. Only then did a neighbor happen to come over to tell me that she had seen them warming their car up in the garage before driving off!

There was enough CO in the attached garage to seep into the house where the sensor was to start this whole boondoggle. So … your advice was absolutely spot on! — Serge

Thanks, Serge. Some houses share a ventilation system with the garage, which makes it even easier for fumes to get into the house.

Other houses with attached garages have an “indoor” quality door between the garage and the house, rather than an “exterior” door that seals well against the weather (and fumes).

So, it’s not worth the risk. Back out of the garage if you want to warm up your car. Better yet, don’t warm it up. Just drive away gently and let the car warm up while you’re driving. That’s also the fastest way to warm the engine.

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