Dear Car Talk:

How long does it take for gasoline to go “bad” in a car’s gas tank?

I have a Kia Optima Hybrid and a Honda Fit. In normal times, I’d fill each one up every week or two, when it got half empty, so there’d always be some fresh gas in the tank.

These days I’m only putting about 3,000 miles per year on each car. I drive each car at least once a week. If I fill up both cars, I can probably go two months (or more) before fill-ups! What’s the best way to manage gasoline usage so it doesn’t go bad? Thanks. — Mark

You have nothing to worry about. Most modern gasolines will easily store for a year.

You may know about the Chevy Volt, which was the first “plug-in hybrid” model on the market, debuting in late 2010. It had both a battery pack, which originally gave you about 35-40 miles on a charge, and a gasoline engine, which could take you a couple of hundred miles more.

We wondered, kind of like you’re wondering, what happens if I own a Volt and I drive less than 35 miles a day — like a lot of people do. In the Volt, you could easily go indefinitely on battery power alone and never activate the gasoline engine.

Well, it turns out the folks at Chevrolet thought of that, too. And they programmed the Volt’s computer so that once the gasoline had been in the tank for a year, it would automatically switch the car to the gasoline engine to empty out the fuel tank and force you to refill it. And they probably erred on the side of caution. So it’d probably be fine for more than a year. Certainly you’ll be fine for two or three months, Mark.

Dear Car Talk: Why is it that my driver’s seatbelt always locks up when I pull it out, and then I have to let it go back in again and try again? — Gregory

You don’t tell us what kind of car you have. Or, more importantly, what year it is. But I’m guessing you’ve got an older car.

Seatbelts have two things to accomplish. Primarily, during a crash, they’re trying to hold passengers in place and spread out the force of impact. That saves a lot of lives. Second, they’re trying to be easy and comfortable to use, so that people will actually wear them and allow those lives to be saved. So seatbelt manufacturers set out to engineer seatbelts that would do both those things.

In the earliest days of shoulder and lap belt combinations, you may remember that the whole thing just kind of hung there, until you draped it across your body. And you had to adjust it for your size, like the seatbelts we still use on airplanes. The problem was, if you wanted to lean forward you had to unlatch the seatbelt in order to free yourself.

So the next step was an automatic seatbelt locking system that allowed people to move a bit while they were belted in. Automatic locking belts were required starting in 1996. They use one of two types of locking retractors. In each case, the seatbelt is wound around a spring-loaded spool, which spins as you pull on the belt.

On your car, Gregory, that spool has a centrifugal clutch. When you pull it slowly, it unspools. But if you pull on it quickly, the centrifugal force of the spinning spool activates a pawl that locks the spool in place.

The idea is that if everything’s fine, and you want to reach the radio to turn off Car Talk, as long as you do it slowly, the seatbelt will unspool and let you move. But if you get in a crash, and suddenly are thrown forward very quickly, the seatbelt will lock up and keep you from getting an indentation on your forehead that says “KIA.” Actually, it would read “AIK.”

The newer type of locking retractor uses an inertial switch, like your airbags use. There’s a small pendulum that detects acceleration and — more importantly in this case — deceleration. On a car that uses an inertial switch, you can pull on the seatbelt as hard or as fast as you want, and it’ll give you slack. But if the car suddenly decelerates — like when you hit the back of a taco truck or slam on the brakes — the inertial switch locks up the retractor and protects you.

In fact, it’s even more sophisticated than that on newer cars. On many cars, the inertial switch fires a pyrotechnic device that actually tightens up the seatbelt and cinches you in place in preparation for impact (called a seatbelt pretensioner), and then lets out some tension milliseconds later, during the crash, to keep the seatbelt from breaking your collar bone or causing chest injuries. We’re even seeing airbags built into seatbelts now to further reduce injuries.

In your case, Gregory, I’m guessing you have an older centrifugal clutch system. Those can fail as they age and lock up too easily. If you can still use the belt by pulling it out slowly, you may just want to live with it. Unless the seatbelt is still under warranty it’ll be expensive to replace.

But if it’s at the point where it takes you 15 tries then it may be time to replace the whole belt, which comes with a new retractor mechanism.

Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.