Q: My 1999 Honda Civic, Kermit, is spinning on to 123,000 miles and still going strong. When I pull into my garage, I pick up a very light scent of something burning. I'm thinking maybe it's my catalytic converter? I've never replaced it.

B.Z., Chicago

A: We seriously doubt that the converter would be the problem. A good mechanic can usually tell what the problem is just by sniffing. We have a hunch your little green car has a minor oil leak somewhere. Start your search at the valve cover.

Q: My car requires premium fuel (91 octane minimum). The price spread between the various gas grades keeps growing. There used to be a dime or two difference between the various grades. Why is premium so expensive?

D.S., Crete, Ill.

A: The U.S. Energy Information Administration (eia.gov) reported that the difference between U.S. average retail prices for premium and regular gasoline reached 50 cents per gallon in late 2016, and it has remained near that level so far in 2017. This price difference, or spread, has been generally increasing since 2000. Many factors on both the supply and demand sides are influencing this trend. The combination of increasing demand for premium gasoline and market challenges to further increases in ethanol blending has led refiners and blenders to acquire more expensive sources of octane, leading to an increase in the price differential between premium and regular gasoline in recent years.

Q: I own a 2007 Ford Explorer Sport Trac with 78,000 miles. Recently, when driving over bumps at slow speeds, three warning symbols always light up: ABS, skidding and wrench. When these symbols are on, the brakes don't feel right and have some vibration. They are OK when warning light symbols go off. The brake fluid is OK, the pads and rotors almost new. No signs of any leaks. Any idea what the problem is?

F.G., Orland Park, Ill.

A: These systems rely on information from the wheel speed sensors. It sounds like you may have a loose wire or poor connection. Otherwise it may be a bad sensor or two. The brakes may feel weird because the antilock brake system (ABS) may be activating.

Q: Can you please explain to me the difference between a sedan, a coupe, an SUV, and a crossover. I enjoy your column, finding it useful and interesting. Thank you in advance.

B.Z., Chicago

A: A sedan is an automobile with four doors. A coupe has only two doors. For instance, the Dodge Charger (sedan) and Challenger (coupe) are manufactured using the same platform. An SUV (sport utility vehicle) is built on a truck platform. For instance, the Ford Expedition (SUV) shares the same platform with the F-150 (pickup truck). Crossover is the term applied to small SUV-like vehicles that are built on car platforms, but typically are taller and have a hatch instead of a trunk.

Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber's work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest Send automotive questions along with name and town to motormouth.tribverizon.net.