Dear Car Talk:

I recently began driving an all-electric car, thinking I was reducing the negative environmental impact of driving. A co-worker has confronted me by saying that I am actually doing more harm than good, due to the rare Earth metals needed for the batteries. He says, furthermore, that when the car has lived out its life, the disposal will be especially troublesome for the environment. What is your opinion? Did I make a mistake by going to an all-electric car? — Paul

I think the mistake you made was listening to that co-worker, Paul. I believe his conclusion is pretty much all wrong.

Electric vehicles (EVs) do not have “zero impact” on the environment; there’s no question about that. But they have less of an impact than gasoline-powered cars. First of all, it’s cleaner and more efficient to produce power at a central location (a power plant) than it is to produce power in everybody’s individual cars.

It’s also easier to clean up, maintain and monitor one smokestack (the power plant’s) than it is to do those things for a million smokestacks (all of our tailpipes). And even if you’re charging your car from the dirtiest power plant, running on 100 percent coal, electric-car expert (and, to be fair, advocate) Jim Motavalli says you’d still reduce climate emissions by 30 to 40 percent over individual gasoline-powered cars.

And, of course, not all of our power plants are run on coal: We have a mix of coal, natural gas, nuclear and, increasingly, wind and solar now. Plus, our power plants have slowly been getting cleaner. And if the whole electric grid continues to move toward cleaner fuels, that will only make the argument for electrification stronger.

As far as the rare Earth metals go, I’m sure there are some ugly things being done as companies dig lithium out of the ground in China, Chile and Australia. But what your friend failed to mention is that all of the batteries that are used in hybrids and EVs today are recycled when they reach the end of their lives.

Those components are still very valuable. So the manufacturer will give you a huge credit for returning the old battery pack when you buy a new one. And it will reuse everything it can.

Then, Paul, there are smaller environmental benefits, like not

having someone’s exhaust blowing into your passenger compartment while you sit behind him in traffic. And not breathing gasoline vapors at the pump every time you refuel.

So I think you are a net positive for the environment. Not to mention that you’re paying a third of the price per mile for electricity that your buddies are paying for gas.

So we would encourage you to feel rightly smug about your electric-car purchase, Paul. Give it a shot.

Dear Car Talk:

I have a 2004 Saturn Vue. Recently I took it in for new tires. While my car was on the lift, it was discovered to have a totally worn-out middriveshaft bearing. There was a 1/2-inch gap of play around it. I wondered how it could be so worn out and not be creating side effects, like noise. When I asked the service manager if the shaft turns all the time, he replied, “Yes.” But now I have had time to analyze it a bit myself, and I think since it is an all-wheel-drive car, the shaft turns only when it goes into

I believe your Vue’s driveshaft turns all the time, Douglas. All-wheel-drive vehicles work in different ways, but I believe the Vue sends power to all of the wheels all of the time.

The bearing for that driveshaft lives inside a rubber housing. So it’s designed to be able to flex a little bit. But if it’s truly worn out, as the mechanic says, you’d feel a wicked vibration at high speeds.

Do you ever drive at high speeds, Douglas? I wouldn’t blame you if you refused to in this car. But next time you do, see if you lose any fillings. Because a worn-out driveshaft bearing would rattle the car very noticeably at highway speeds.

If you don’t notice a vibration at high speeds, then you probably don’t need to do anything. Maybe the mechanic mistook the built-in flex for a worn-out bearing — a half-inch is probably about right. Or maybe it really is wearing out but isn’t bad enough to replace yet. Or perhaps the guy just had a boat payment due that week.

But if it makes you feel better, get a second opinion. Hopefully it’ll be something besides “... and your car is ugly, too.” Good luck, Douglas. all-wheel-drive mode. For me, that is almost never. Can you tell me the true story on this? — Douglas