Though gasoline prices are not expected to reach the levels they did at this time last year, when regular cost more than $2 a gallon at many Chicago stations, prices are again fluctuating for that unleaded liquid.
Prices in Illinois now average $1.507 a gallon, which is up slightly from last month’s average of $1.500 a gallon.
When gas prices rise, motorist’s moods turn sour. Even well-to-do owners of humongous, gas-guzzling, luxury sport-utility vehicles get concerned about fuel economy. So, to combat those costs, let’s review the causes of and corrections for poor fuel economy.
There are two fundamental reasons for poor fuel economy: Inorganic and organic.
The inorganic category comprises all the things about your vehicle that contribute to decreased mileage. The organic category refers to you and your behavior.
Inorganic
Routine maintenance is the first step to keeping your car as fuel efficient as possible.
Oil’s viscosity increases over time. And thick oil not only creates internal drag on your engine, it also does a poor job of lubricating, increasing friction. If neglected too long, your engine begins to wear internally. Valves don’t seal as tightly. Piston rings wear and allow blow-by of combustion gases and unburned fuel. Cam timing gets sloppy.
As spark plugs age, their gaps widen. When that happens, it takes more electrical energy for the spark to jump the gap. If the plugs are very worn, the spark may not jump and your engine will miss. One failed plug in a 4-cylinder engine means that 25 percent of your engine is not doing its job.
A car out of alignment scrubs along. Dragging brakes are doubly costly.
You may not feel the effects, but a sluggish oxygen sensor makes the engine use more gas than necessary. Dirty fuel injectors and carbon-coated valves or pistons can reduce your mileage.
An exhaust restriction, from a failing catalytic converter or collapsed double-wall exhaust pipe, keeps your engine from breathing freely and running efficiently. Ditto for a dirty air filter.
Fuel choice also may affect your mileage. If your car calls for premium, using a lower octane may cause engine knock. A knock sensor detects it, and the computer retards the ignition timing, making the engine run less efficiently. If your car runs fine on regular, switching to premium won’t improve your fuel economy.
Organic
The human factor far outweighs the mechanical when it comes to wasting gas. Short trips, especially if the engine doesn’t get a chance to warm up, waste gas because the engine runs rich.
Jackrabbit starts, as everyone knows, waste gas. So does idling; at idle, you get zero miles per gallon. High-speed dashes from traffic light to traffic light are foolish. Stop-and-go driving bedevils gas mileage, but driving gently can mitigate the problem.
Obviously, towing a trailer will affect fuel economy, but do not overlook the effect of other unnecessary weight. For every 125 pounds, you pay a 0.3 percent penalty in gas mileage so take your anvil collection out of the trunk.
And, there are other “loads” that rob gas mileage. They include the air conditioner, the rear-window defogger, lights and anything that puts an electrical load on your car. As a rule of thumb, for every 10 amps of draw, you lose one-half mile per gallon.
Resting your foot on the brake pedal not only creates drag, it also wears out your brakes prematurely and annoys the driver behind you.
Stuff on the roof also is a drag, literally. Car-top carriers and ski racks add wind resistance that the design engineers work to reduce. At highway speeds, open windows also can create drag, so using the air conditioner imposes a smaller fuel-economy penalty than open windows.
Higher speeds also reduce fuel economy. There is a geometric increase in wind resistance that is more than proportional to the increase in speed, so traveling 65 m.p.h. reduces fuel-economy 15 percent from 55 m.p.h., but speeds less than 55 m.p.h. don’t save significantly more fuel.
Choosing the right speed but the wrong range on your automatic transmission selector clashes with the best economy. Selecting Drive instead of Overdrive may cost you 3 to 5 miles per gallon.If you don’t know how to select overdrive, check your owner’s manual. If you have a manual transmission, shift to the next higher gear as soon as possible without lugging the engine. If you have a shift light, it will come on when it’s best to shift for best fuel economy.
You may have ridden with someone who cannot keep the accelerator pedal steady. Every time that foot jabs the pedal, an extra shot of gas goes to the engine. It also may cause the transmission to downshift or, at least, drop out of overdrive. This can cause a transmission hunting sensation and increases gas consumption. Ease on the gas, coast to a stop as much as possible, then ease on the brakes.
The greatest fuel savings device is the world is attached to the end of your right leg.
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Tips to save gas and money.
Getting better mileage is one way to fight the sting of high gas prices. Here are some tips to help you do that:
FUEL ECONOMY
When buying a car, consider the mileage. The driver of a 19 m.p.g. car spends $1,263 for fuel a year at $2 per gallon and would save $558 if the car got 34 m.p.g. (Based upon an average of 12,000 miles a year).
0.5%
TIRES
Check your tires. Underinflated tires can cut fuel economy by a half-percent per pound of pressure below recommended levels.
0.3%
CHECK CARGO
Pare extra weight. For every 125 pounds you carry, you reduce your mileage by 0.3 percent.
40%
OXYGEN SENSOR
Check your emissions. For instance, if your car is noticeably out of tune or has failed an emissions test because of a faulty oxygen sensor, the repair may improve your gas mileage-up to 40 percent depending on the type of repair and how well it is done.
1-2%
OIL
Use the right oil. You can improve your gas mileage by 1-2 percent by using the manufacturer’s recommended grade of motor oil.
10%
AIR FILTER
Keep it clean. Replacing a dirty air filter can improve your car’s mileage by as much as 10 percent.
50%
TUNE-UPS
Stay in tune. A poorly tuned engine can increase fuel use by up to 50 percent.
5%-33%
WHILE DRIVING
Drive smoothly. Aggressive driving (speeding, rapid acceleration and braking) wastes gas. It can lower your mileage by 33 percent at highway speeds and 5 percent around town.
Sources: AAA, Environmental Protection Agency, U.S. Department of Energy, Sierra Club.
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Bob Weber is an ASE-certified Master Automobile Technician, having recertified every five years since 1978. Contact him at MMTribune@netscape.net.
