Dear Car Talk:

Where I live, in the People’s Republic of California, gas costs much more than anywhere else. For instance, I recently saw 87 octane for $3.60 a gallon, 89 octane for $3.80 a gallon, and premium 91 octane at $3.90 a gallon. My wife’s older Lexus LS400 runs nicely on 89 octane. Here’s my question: If I buy 89 octane, it costs me $3.80 a gallon. What if I put in half a tank of 87 octane, and half a tank of 91 octane? Would I get 89 octane at 5 cents less per gallon? Inquiring minds would like to know. — Tom

Yes. You’ve broken the code, Tom. But now that the oil companies know who you are, prepare to see your face on a wanted poster in every Exxon station bathroom.

This is, in fact, exactly how most gas pumps deliver 89 octane fuel. When you choose 87 octane, it gives you fuel from the 87-octane storage tank below the pumps. When you choose 91 octane, you get fuel from the 91-octane tank.

But when you choose 89 octane, the gas pump literally just blends the two fuels as it sends it into your gas tank, giving you half of each, which gives you 89 octane.

So you can do exactly the same thing yourself, and save 5 cents a gallon. The only thing it costs you is your time. But we can calculate that, too.

Let’s say your tank takes 20 gallons of fuel. You start with the 91 octane and you add 10 gallons. Then you stop, turn off the pump, and start again.

Of course, now you have to reenter your credit card, enter your ZIP code, submit your fourth-grade report card, choose the 87 octane, and wait for the pump to turn on again.

Let’s say that adds an extra three minutes to your refueling time. With 5 cents off every one of your 20 gallons of fuel, you save a total of a dollar. A dollar every three minutes is the equivalent of $20 an hour.

So if your time is worth less than $20 an hour, you’re in the black, Tom. Just don’t forget to factor in the dollar in time you just wasted reading this answer, too.

Dear Car Talk:

When I purchased a new Saturn SL in 2002, I had no idea that it would still be running 333,333 miles later.

While it has needed regular maintenance, it has never stranded me or failed to get me to my destination. It even

has its original clutch and rear brakes.

I’m now getting grief from family members who don’t appreciate my Saturn’s longevity. They assume that any vehicle with so many miles must be a heap to be avoided.

How can I bring enlightenment to these nonbelievers? Or am I just too cheap to purchase a new vehicle to make them happy? — Pat I’m going with option 2, Pat.

You never expected your 2002 Saturn to last 333,333 miles. And neither did Saturn. To be fair, we do get occasional letters from Saturn owners who have very-high-mileage cars and who sing their economic, if not aesthetic, praises.

I tend to think those rare, highmileage Saturns have more to do with the owners themselves, who are very conscientious, gentle drivers and would probably make any vehicle they drive last for decades. But that’s a PH.D. thesis for another day.

If the vast majority of your driving involves short trips and low to modest speeds, there’s no reason you couldn’t keep driving your old Saturn if you want to, Pat.

But I doubt you’re just moseying around town. Why? Because, according to my calculations, you’re driving about 20,000 miles a year. And what you’re missing during all those hours every day you spend in that car are the vastly improved safety features that newer cars now have.

Structural protection is better. There are airbags galore in modern cars — side bags, head bags, knee bags, wind bags. Oh, wait, that’s me.

There’s automatic emergency braking that applies the brakes if you don’t see a hazard and react in time. There’s lane-keeping assistance that nudges you back between the lines if you drift. There’s blind spot monitoring that tells you if someone is pulling up alongside you on either side.

You may be more enlightened, Pat, but you’re less safe than the relatives who are urging you to update your wheels — either out of love or, more likely, embarrassment.

Or maybe it’s the aroma in the car that your relatives can’t stand, Pat. You may have become inured to the Saturn’s old car smell sometime during the past 250,000 miles. And we haven’t even mentioned the improvements in pollution controls or fuel economy. Or the seat and steering wheel warmers.

If you do decide to upgrade (and rest assured, you’ve gotten every penny out of your Saturn), be sure to get every available safety feature on your new car.

It’s likely you’ll be writing to us again in 2037 asking if you really need to upgrade your 2020 Kia to a batterypowered hovercraft. And loading up on the latest safety equipment will put off your next rendezvous with obsolescence a little bit longer. 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.