•Q. I have painful, incapacitating sciatica on the left side, most likely from constantly engaging the extremely hard clutch in my 2000 Toyota Celica. Have you heard of this association? I’m wondering if the clutch can be adjusted so that it’s looser. Or, if not, how should I go about finding an easier-to-clutch used car with manual transmission that is not a lemon or too costly to maintain?•

RAY: We’re not doctors ... although my brother does make the other mechanics at the shop work in hospital johnnies every week as part of Casual Friday.

TOM: That’s just to give the customers some laughs. And because they find the open-back design to be cooler in the summer.

RAY: You can’t adjust the feel of the clutch. Assuming it’s always been like this and didn’t suddenly change, it is what it is. In fact, we’ve always found Toyota clutches particularly light and easy to shift.

TOM: So forget about making an appointment with your mechanic. Instead, make an appointment with a good physical therapist. On top of that, we’d recommend several other things if we were your medical-automotive advisers:

RAY: No. 1, get a car with an automatic transmission. If a clutch is causing you incapacitating pain, why not eliminate that from your life? Even if it’s not the cause of your sciatica, it’s got to make it harder and less comfortable for you to drive.

TOM: So, your next car should be an automatic. It also should have a power driver’s seat. In our extremely limited knowledge of lower-back issues, seating position and the angle of your legs vis-a-vis your torso make a great deal of difference.

RAY: So it might not be the clutch in the Celica that caused your sciatica; it might be that the seating position is so low that your legs are folded up and putting strain on your lumbar spine.

TOM: I like how you threw in the term “lumbar spine” there. Makes it sound like you almost know what you’re talking about.

RAY: Thanks. If you have a power-adjustable seat, you should be able to raise the height of the seat, which changes the angle at which your legs are sitting. The more seat adjustments you have available to you, the better the chance of finding a comfortable, less painful driving position.

TOM: So I think you need a different car. And if you’re looking for a used car, you might want a copy of the pamphlet we wrote called “How To Buy a Great Used Car: Things Detroit and Tokyo Don’t Want You To Know.” (To order, send $4.75 (check or money order) to Used Car, P.O. Box 536475, Orlando, FL 32853-6475). That contains our best advice for finding and inspecting a used car.

RAY: But whether you go new or used, go automatic. And go with a power seat. And go see a physical therapist. Good luck. Hope you feel better.

•Q. We bought a brand-new Mini Cooper S. Nobody told us what grade of gas to run it on. Stupidly, we did not look in the manual. We ran it on 87 regular for a little more than a year. When we brought it in for service recently, the dealer told us to run it on 91. Did we ruin the car? The dealer told us we most likely have valve carbon build up. There was no knocking or stalling. I am freaking out that we put a hole in a piston! It is my wife’s car, and she loves it. Please help! Thanks for your advice.•

TOM: Have you ever considered switching to decaf?

RAY: You can stop freaking out. You didn’t put a hole in a piston. If you had, you would have noticed immediately that the car sounds and shakes like one of my brother’s cars.

TOM: Your car’s engine-management system actually adjusts for the grade of gasoline you put in it.

RAY: In the old days, if your car needed 91 and you used 87, you would have caused the engine to “knock” on hard acceleration, on hills or in high heat. That knocking was the sound of pre-ignition, or gasoline igniting when it wasn’t supposed to. That could cause damage to the engine over time. Even in the short run, it could harm things by making your engine run hot.

TOM: But since engines are now managed by computers, yours has what’s called a “knock sensor.” Guess what that does? It senses knock! And if it detects a grade of fuel that’s lower than what’s recommended, it adjusts the car’s ignition timing to make up for it and avoid damage.

RAY: So, why wouldn’t you just use 87 all the time, and save a lot of money on gas? Well, in cars that “recommend” premium fuel, like yours, you can. And I would. Manufacturers say you may notice a small drop in fuel economy and a slight decrease in power, but it’s not enough for most people to notice.

TOM: On the other hand, some cars say they “require” (rather than “recommend”) premium fuel. In those cases, you’re stuck. So our advice is to ask for a look at the owner’s manual, and check a car’s fuel recommendation before you buy it!

RAY: But doing what you did caused no damage at all. Zip. Nada.

TOM: So, for your own mental health, I suggest that you forget this whole incident ever happened. If you have trouble letting it go, I suggest going to see your Mini dealer’s in-house hypnotist. He’s conveniently stationed next to the cashier at the service department’s pick-up window.

Got a question about cars? Write to Click and Clack in care of this newspaper, or email them by visiting the Car Talk website at www.cartalk.com.