MAGLIOZZI

Dear Car Talk: I’ve been driving cars that take regular gas for more than 30 years. I just purchased a brand-new car that takes premium gas, and I may have screwed up. The first time the car needed gas, I filled up about half the tank with premium gas at a more expensive gas station near me. Then drove to a place where it’s much cheaper (same “brand”) and filled it up the rest of the way.

I’m concerned that at the second gas station, I may have pressed the “regular” button instead of “premium” — ugh! (Dope slap!)

Have I done any damage to my car? And should I plan on driving until my tank is pretty much empty before filling it with premium (provided I remember)? — Creature Of Habit

Oh, my goodness. This new car is ruined, Creature of Habit. But as a favor, I’ll give you $500 bucks for it.

No, your car is going to be fine. Check the notice on the inside of your gas cap cover. It’ll either say “Premium Fuel Recommended” or “Premium Fuel Required.” There’s a difference.

If it says “recommended,” then your car is designed to run on pretty much any grade of gasoline. All cars have knock sensors these days. And if the knock sensor detects a lower octane fuel by picking up signs of pre-ignition, it’ll signal the computer to adjust the engine parameters — like the ignition timing — to run safely on that lower-octane fuel.

You may experience a slight decrease in power and mileage, but the car will be completely unharmed. And if the changes are undetectable to you, you can opt to save the 30 cents a gallon at the pump every time.

On the other hand, if you’re driving a $160,000 Porsche or other high-performance car, you may see a notice that reads “Premium Required.” In that case, you should regularly fill the tank with premium. Cars with very high compression ratios and powerful turbochargers can reportedly be harmed over time if they’re forced to run continuously on lower-octane fuel.

But even those high-end cars have knock sensors designed to accommodate lower-octane fuel. So, putting a tank of 87 octane in your BMW 7-Series every once in a while is not going to do any damage to the engine. It’ll adjust to the fuel and be fine.

Of course, if you’re still worried about it, keep my $500 offer in mind.

Got a question about cars? Write to Ray in care of King Features, 300 W. 57th St., 41st Floor, New York, NY 10019, or email by visiting the Car Talk website at www.cartalk.com.