•Q. I just bought a new Mazda, and the owner’s manual states that I should use 0W-20 oil. I wonder if that is too lightweight for summer travel at interstate speeds, and would it not cause the engine to wear more than using 5W-30? The vehicle is a CX-7 with a 2.5-liter I-4 non-turbo engine. I like getting 100,000-plus miles on my vehicles: I currently have an ’03 Protege with 120,000 miles and a ’97 Toyota with 140,000, and I would want this CX-7 to get that kind of use. Please advise on your feelings about this 0W-20 oil.•

RAY: It’s good stuff. My brother uses it in salads.

TOM: For years now, car manufacturers have been pressuring oil companies to make oil better and less viscous. And they’ve done it.

RAY: Just because oils are less viscous (thick), that doesn’t mean they don’t lubricate, dissipate heat or protect well against wear and tear. It just means they do all that stuff while creating less friction, which means you get better mileage and longer engine life.

TOM: You’re probably not old enough to remember when cars routinely took 40-weight oil in the summer and 20-weight oil in the winter. That stuff was real sludge. You could still see the dinosaur bones in it.

RAY: Then, multi-viscosity oils were invented. So, for instance, you could use a 10W-40 oil that would act like a 10-weight (thinner) oil when the temperature was low and a 40-weight (thicker) oil when the temperature was high.

TOM: And, through the years, as lubricant technology has improved, the viscosity of the oils has dropped, to the point where we can now use a zero-viscosity oil in cold weather. That means the engine uses less energy to push its parts through the oil. That energy goes into miles per gallon instead.

RAY: It also means the oil coats the inside of the engine more quickly — in a fraction of a second after startup — which protects the engine from wear and tear during cold starts, and makes it last longer. It also means the engine starts more easily in cold weather. Pretty good stuff, huh?

TOM: We’ve seen no problems as cars have gone from 10W-40 down to 5W-20. And while the 0W-20 is fairly new, I don’t expect any problems from that, either.

RAY: That said, most vehicles have “severe duty” recommendations in the owner’s manual. They’ll tell you that if you’re planning to climb Pike’s Peak with a trailer, if you’re using your car as a taxi or if you live where it’s regularly above 100 degrees out, you qualify for special maintenance procedures. Those can include more-frequent oil changes and/or use of a different oil.

TOM: So, if that describes you, check your owner’s manual and look up the severe-duty recommendations. But if you’re just driving the car like the rest of us, I’d go with what the manufacturer suggests.

•Q. My question concerns the “lube” portion of “lube, oil and filter.” A couple of years ago, I took a new job that is a mere four miles from my home. Between the short driving commute and bicycling to work, my car sees few miles and spends a lot of time in the garage. This has been good for both my waistline and my wallet, since my insurance company offers a low-mileage discount. However, this also means that I go a long time between lube, oil and filter services. Instead of every three months, it may take me six months to put 3,000 miles on my car. And with you guys preaching longer times between oil changes these days, I could conceivably go nine to 12 months between lube, oil and filters. This may be fine for the oil and filter, but should the undercarriage and chassis of a car be lubricated more than once a year? When I do take the car out for longer trips, I can hear squeaks, and it feels stiff (or this could just be my imagination). Should I have the car lubed every three or six months, even when it doesn’t need its oil and filter changed? Thanks!

TOM: When you take your car into the shop these days, there’s really not much for the mechanic to lubricate — other than your credit card, to make sure it swipes nice and smoothly.

RAY: On modern cars, things like ball joints are all permanently sealed at the factory now. So when you look at most maintenance schedules, there’s almost nothing that calls for lubrication.

TOM: There are lots of trucks that still have grease fittings on ball joints and tie rods, but we hardly ever see cars that take grease anymore.

RAY: In fact, the only use our old grease gun gets anymore is juicing up the toilet seat on April Fool’s Day.

TOM: However, if something specific is wrong, certain parts can be lubricated to try to address the issue. For instance, if a customer comes in with a stiff, squeaky door, we’d obviously lubricate the hinges.

RAY: Or if a customer with an older car complains that it’s creaking when it goes over bumps, we’d start by lubricating the control arm bushings, and maybe the stabilizer bushings, too.

TOM: Those bushings can dry out over time, and they often respond to an application of good penetrating oil. You might want to have your mechanic try that for you.

RAY: But if you do that once, it should be good for years. There’s no reason to do it every three or six months. So just base your maintenance visits on when you need an oil and filter change, and forget all about the word “lube.”

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.