See more of the story

Q: We recently purchased a 2016 Honda CR-V four-cylinder and there is only one thing that we are dissatisfied with. Oil changes are required every 3,750 miles and we have not found out why. We have been living with Toyotas for years with a 5,000-mile change requirement and the new mileage seems awfully low. Is it a new engine or an attempt to make more money in the shop?

T.M., Bethlehem, Pa.

A: Where did that oil change schedule come from? Your vehicle has a maintenance reminder system that alerts you when service is due. Even older Honda oil change schedules were 7,500 miles or once a year, whichever came first. If you want to change the oil every 5,000 miles, bully for you! Don't forget to reset the maintenance reminder, though.

Q: I have a 2006 Saab 9-7X with 72,000 miles. While braking, I hear a scrunching noise that sounds like my antilock brakes are kicking in. This only happens at the lowest speeds. It happens on wet or dry pavement and the ABS light does not come on. I had the vehicle checked out by my local mechanic, who could not identify the cause. He said that the rotors were rusty and the brake pads were only 50 percent worn. He was willing to replace the pads and rotors for $350, but did not feel that this would solve the problem. He said the vehicle is perfectly safe to operate. Should I check with another mechanic?

W.C., Willimantic, Conn.

A: The issue could very well be the ABS system. And, it may be as simple as cleaning the wheel speed sensors. This is rather common on the Saab 9-7X, especially in the Snow Belt. One of the sensors may be faulty or corroded. If cleaning them does not help, further diagnosis is required and the sensors may have to be replaced.

Q: Does a block heater heat all the coolant? Does it circulate warm water through the heater core? I think not. After you start the engine you must continue to heat the rest of the coolant. That won't begin until the thermostat opens.

J.D., Syracuse, N.Y.

A: Due to thermal dynamics, the coolant does circulate, albeit slowly. Energy seeks a state of entropy — thermodynamic equilibrium. Warmer, highe- energy molecules will move toward cooler, lower-energy molecules. In other words, it attempts to even out. Engine heat, aided by circulation from the water pump, makes a big difference. But before the thermostat opens, coolant is circulated though a bypass circuit that includes the heater core but not the radiator.

Q: My maintenance manual states the 16 spark plugs for the 2012 Chrysler with the Hemi 5.7-liter engine should be replaced every 32,000 miles. I have about 44,000 miles on the vehicle and have not replaced the spark plugs. The vehicle performs great — just like the day I purchased new some four years ago. Your thoughts?

R.T., Lincolnshire, Ill.

A: As things such as spark plugs wear, the engine control computer will compensate as much as possible so that the owner has no major problems and the emissions do not become excessive. But there is a limit, so you should perform all maintenance according to the schedule in your owner's manual. It is best not to take the risk.

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