Motormouth: How much gas is wasted by idling?

McClatchy-Tribune Information Services

March 19, 2018

Q: With the engine idling, how long does it take to consume a gallon of gasoline? Im asking because I wonder if shutting off the engine at stoplights actually saves anything or if it is simply hype.

G.E., Crystal Lake, Ill.

A: Based on work developed by Argonne National Laboratory, the idle fuel consumption rate with no load (no use of accessories such as air conditioners, fans, etc.) varies widely. Compact cars with 2-liter engines consume about 0.16 gallons per hour. A large sedan with a 4.6-liter engine consumes just over twice as much fuel at idle, or over a quart. That may not sound like much, but carmakers are seeking ways to save every extra drop of fuel to meet federal corporate average fuel economy standards.

Q: As a teenager in the 1960s, I learned to drive in a car with a column-mounted three-speed manual gearshift. What year was the last American car with a "three on the tree?" Are the modern transmissions cheaper to produce, provide better economy or are they safer? Or is the customer just too lazy to be bothered by the physical effort needed to change gears?

B.P., Cedar Rapids, Iowa

A: Wikipedia reports that the column-mounted manual shifter disappeared in North America by the mid-1980s, last appearing in a 1987 Chevy pickup, if you can trust Wikipedia. Sadly, most Americans prefer automatic transmissions. Perhaps it is because shiftless kids never learned to use a manual shifter or, as you suggest, they are simply too lazy. For what it is worth, Mrs. Motormouth refuses to buy a car unless it has a stick. Maybe her next car will be a Dodge Challenger Hellcat.

Q: I have a 2009 Lincoln MKZ with almost 100,000 miles. When I put it in reverse a beep warning alarm goes off if it is about to make contact with some object. When I backed the car out of the driveway a few days ago a dashboard light came on saying to check the "parking aid assist." I took it to a dealer who said it might need a computer module that would cost $2,500 and that it would cost $100 to run the test to determine what the problem actually was. Spending up to $2,600 to fix a backup alarm buzzer sounds ridiculous to me. Any suggestions for a less expensive solution?

R.S., Coral Springs, Fla.

A: One simple solution is to install an aftermarket backup camera. Many of them simply mount to the license plate frame and are wired into the backup lights to power them in reverse. Recently, however, there has been an explosion of self-powered (battery) backup cameras that use a smartphone to display the image to the driver. No wires attached! Not only is this less expensive than repairing your warning system, it updates to the current backup technology.

Q: During the course of a 20-minute highway drive it is not unusual for me to see four cars with a single headlight and Im being careful not to count motorcycles. It does make for a good game of Padiddle though!

C.T., Berwyn, Pa.

A: Weve heard that Padiddle started out as a kissing game, but morphed into being the first to touch the cars ceiling (or punching your brother) when spotting an oncoming car with only one headlight. We are not sure what is causing the phenomenon you report, but we would like to remind our readers that when one light goes out, you should replace both. After all, they are the same age and the second may soon fail.