Q: What does it mean to buy a certified car? When I got my used 2018 Toyota Camry SE nearly a year ago, they played up the certified car bit. I tried to get an explanation from the dealership manager and others about what that meant, but no one had an answer. In their shop, no one can answer questions regarding the information on my dash screens. It also jerks when changing gears, but they won't look at it.

A: Certified Previously Owned (CPO) cars usually have fewer miles and might have had better care. They usually have extended warranties. CPO cars pass a multipoint inspection to verify that repairs are not imminent. Of course, you will pay a little more for this, but the increased reliability usually is worth it.

Did you buy the car from a Toyota dealer? It sounds like you were taken by a not-so-honest used car lot. (That they don't understand the data on the dash screens is another red flag.) Independent dealers can slap a CPO sign on anything. And in those cases, it's meaningless.

No need to overspend

Q: I wonder if the Intelligent Oil-Life Management (IOLM) 10,000-mile standard set forth in the owner's manual can be trusted. Will it protect the engine as well as the 5,000 mile-standard the dealer recommends? Also, does my decision affect the warranty.

A: Yes, oil life monitors can be trusted. Automobile manufacturers don't want people to stop buying their vehicles because they break down, so they are careful to put the best information in the owner's manuals. Following the recommendations saves you money while reducing the amount of petrochemical waste. Neither following the monitor nor changing the oil more often will affect the warranty.

Oil flip-flop no problem

Q: I own a 2010 Toyota Tacoma truck with 42,000 miles. Several years ago, when I had an oil change, the dealership put in synthetic oil instead of regular oil. A couple of months ago, the dealership did the same thing. Will it damage my vehicle to go back to regular, or should I just stick with synthetic?

A: You may use synthetic oil exclusively if you like. But if you want to switch back to the traditional oil recommended in the owner's manual, there will be no harm.

Testing testers

Q: Owning a truck, SUV and four motorcycles, I've come to the realization that I need a competent battery tester. I want one that places a load on the battery. An online search reveals that Ancel and Foxwell products get lots of good reviews. Any thoughts?

A: I like handheld testers, but having used only a professional Ancel unit, I cannot vouch for any particular over-the-counter brand. The best thing about these little tools is that the battery need not be removed for testing.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician. His writing has appeared in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.tribune@gmail.com.