Tuesday, October 17, 2006

Do Any Gas Saving Gadgets Really Work

When I originally wrote this piece, the price of regular grade 87 octane gasoline was almost $3.40 a gallon in the metro Chicago area. The huge jump in fuel prices ihit motorists hard. People started looking for ways to reduce their fuel costs. Some were trading in their big gas-guzzling SUVs for smaller vehicles. More people switched to public transportation and car pooling (both of which are almost as painful as paying more at the pump). And some fell victim to con artists selling gas saving gizmos that promise huge fuel savings.

As PT Barnum once said, "There's a sucker born every minute." So don't fall for the con artists lies. Forget the gas saving gizmos because none of them work!

Every gas saving gadget I've seen to date does absolutely NOTHING to improve fuel economy. In fact, some of them actually reduce fuel economy.

Products that claim to magnetize or polarize gasoline molecules, realign the molecular structure of the fuel for more efficient combustion, or ionize the spark for better mileage are pure nonsense and are based on false science. So are products that swirl air entering the throttle body or leak air into the intake manifold to improve fuel efficiency. None of these product produces any measurable improvement in fuel economy.

100 mpg carburetors or fuel injection systems? Pure science fiction and urban legend.


One gas saving gadget that can improve fuel economy is a simple vacuum gauge. The gauge displays intake vacuum, which is an indication of how much load is on the engine. The lower the vacuum reading, the higher the load on the engine and the more fuel it burns.

The gauge saves gas by helping the driver see the effect his right foot has on fuel consumption. Tromp down on the gas pedal and intake vacuum drops and fuel consumption goes up. Take it easy on the gas pedal and accelerate slowly causes less of a drop in intake vacuum and less fuel usage. Duh! Pretending there is a raw egg under the gas pedal can have the same positive effect on fuel economy.


Back in the days when carburetors were used to feed gasoline into the engine, there were a couple of tricks that could improve fuel economy a bit, especially when the engine was cold. One was a simple honeycomb spacer that fit under the carburetor. The turbulence created by the honeycomb helped break up the fuel a bit. Another was an ultrasonic vibrator that mounted under the carburetor. The vibrator also improved fuel atomization slightly -- but only provided a marginal benefit when the engine was cold.

Some engines from that period used an electrically heated grid under the carburetor to improve fuel atomization following a cold start. But like the other devices, the benefit disappeared once the engine reached normal operating temperature.

Today's fuel injected engines atomize the fuel when they spray the fuel into the engine. They don't need intake manifold heaters or other such devices. The most efficient designs are the new high pressure "direct injection" systems that VW uses on some of its engines.


Other fuel saving tricks that actually work include variable displacement on demand (which is used on the new Chrysler Hemi engines in the 300C and other models), and the start/stop systems that some of the new GM and Ford hybrid vehicles have to turn the engine off when the vehicle sits for more than a few seconds at a stop light to save fuel. Fuel savings attributed to these technical improvements range typically from 5 to 15%.

The most fuel efficient cars currently on the road are ones like the Toyota Prius (50 to 60 mpg city) and Honda Civic hybrids that use a combination of electric power and gasoline power to optimize fuel economy.

The most fuel efficient vehicles of all were GM's discontinued EV1 electric cars, which used no gasoline at all. GM built about 1,000 of these two-seat cars and leased them to motorists in California. Almost everybody who drove one said they loved it. Unfortunately, these cars were introduced a few years too soon and were discontinued because of limited range (about 100 miles on a full charge), and the high cost of the batteries (GM's cost was reportedly $500 for each battery, and each car held 18 batteries!). If GM were to re-introduce the EV1 today, buyers would be standing in line and paying full list price plus -- just like people who want to buy a Toyota Prius today.


Miracle friction-reducing oil treatments are also a scam. Many of these products contain Teflon, which is claimed to have a coating action that reduces wear and friction. General Motors evaluated some of these products a number of years ago using an electron beam microscope to examine engine parts after the engine had been run with the special treatment. Guess what? They couldn't find a trace of the stuff on any of the metal parts. The Teflon ended up in the oil filter and the bottom of the oil pan.


The only way to reduce internal engine friction is to run a lower viscosity oil with a "fuel saving" rating from the American Petroleum Institute (API). Switching from a 10W-30 to a 5W-30 or 5W-20 oil may improve fuel economy a few tenths of a percent, but that's about all the improvement you're going to get.


A dirty air filter that is clogged with debris will restrict airflow into the engine and hurt fuel economy, performance and emissions. Inspect the air filter and replace it if it is dirty. The photo at the top of this page shows an air restriction gauge that indicates when the air filter is dirty and needs to be replaced.

How can you tell if the filter is dirty? Hold it up to a bright light. If the filter element is dark and obstructs most of the light, the filter needs to be replaced.

Stock air filters flow just as much air at low to mid-range engine speed as most aftermarket "performance" air filters. Installing a less restrictive performance filter may improve performance slightly at high engine speed, but for normal driving it probably won't have any measurable impact on fuel economy.


Ignition misfire can waste a lot of fuel and cause a big increase in exhaust emissions. On 1996 and newer vehicles with OBD II, the engine management system is capable of detecting engine misfires and will turn on the Check Engine light and set a diagnostic trouble code (P0300 series) if it detects a misfire problem.

Misfire can be caused by worn or dirty spark plugs, high resistance in spark plug wires, a weak ignition coil, dirty fuel injectors, low fuel pressure (weak pump or dirty fuel filter), or compression problems (burned valves, weak or broken valve springs, leaky head gasket, rounded cam lobes).

Standard spark plugs should be replaced every 45,000 miles, while platinum or iridium tipped long-life spark plugs can typically go 100,000 miles before replacement is needed. Refer to your owners manual for the recommended replacement interval.

Some spark plugs have special electrode configurations that are designed to minimize misfires. These may have a marginal benefit on fuel economy and performance, but don't expect any miracles.


A less restrictive exhaust allows the engine to breathe easier and use less fuel. Replacing a restrictive stock muffler with an aftermarket performance muffler can reduce backpressure and improve performance and fuel economy slightly. But the trade-off is usually a significant increase in exhaust noise.


One way you can maximize fuel economy is to keep you tires properly inflated. Increasing tire pressure reduces rolling resistance, but also adds ride harshness. For most cars, 32 to 34 psi is the maximum recommended inflation pressure for average driving. Refer to your owner's manual or the tire inflation decal in the glove box or door post.

Never exceed the maximum inflation pressure printed on the tire sidewall. Overinflated tires ride rough and increase the risk of tire damage or tire failure!

Underinflated tires, on the other hand, increase rolling resistance and drag. This makes the engine work harder and uses more fuel. Low air pressure also increases flexing of the tire's sidewall, which makes the tire run hot. Driving on a low tire at high speed on a hot day or with an overloaded vehicle increases the risk of tire failure and a sudden blowout. Never drive on tires that contain less than 25 psi of air pressure.

Air pressure should be checked at least once a month, and every week if you do a lot of highway driving. The pressure should be checked BEFORE the vehicle is driven because driving increases the temperature of the tires and the air pressure inside. If a tire is low, use a foot pump or compressor to add air. Then recheck the pressure to make sure it is correct and is not overinflated (this is especially important when using a high pressure hose at a service station). Also, use an accurate gauge. The gauges on many tire inflation machines are out of calibration.


Lightening a vehicle by removing unnecessary junk from the trunk or cargo area can also improve fuel economy a bit. But don't toss the spare tire or jack because you may need these items down the road.

Getting the lead out of your own posterior can also help. Walk more and drive less. Ride a bike. Go on a diet. Every 10 lbs. of fat you lose is 10 lbs. less dead weight your engine has to push down the road.

Keeping your gas tank half full is another trick that can save some weight. Gasoline weighs about 6.2 lbs. per gallon (6.3 lbs. for premium), so keeping a 20 gallon tank h`lf full saves about 62 lbs. of weight. Don't run the tank too low, however, because that may shorten the life of your fuel pump. Most engines with electronic fuel injection have an electric fuel pump mounted inside the gas tank. The pump runs hot and needs a certain amount of fuel for cooling and lubrication. Running out of gas may damage the pump and end up costing you $300 to $600 to have a new one installed!

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