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How to Improve Fuel Economy


When fuel prices are high, motorists get serious about looking for ways to improve fuel economy and reduce their fuel costs. Some trade in their big gas-guzzling SUVs for smaller vehicles. Some people actually switch to public transportation or car pool. And some fall for fake gas saving products that make big claims but deliver little if any real savings.

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. The U.S Environmental Protection Agency has reviewed dozens of these gas saving devices over the years and has yet to find a single one that improves fuel economy.

Products that claim to magnetize or polarize gasoline molecules, or realign the molecular structure of the fuel for more efficient combustion (cow magnets and similar gadgets), or devices that claim to ionize the spark for better mileage are pure nonsense and are based on false science.

What about devices that swirl air entering the throttle body and "supercharge" your engine? These devices are installed in the air inlet system and have a blade that supposedly swirls the incoming air to improve fuel atomization for more efficient combustion. Baloney. Several car magazines have tested these devices and found they actually REDUCE horsepower and fuel economy by creating a restriction in the air intake system.

What about the infamous 200 mpg carburetor? By vaporizing the fuel, this carburetor is claimed to deliver 200 plus miles per gallon on any engine. Pure urban legend. Check it out on Snopes. Actually, direct fuel injection vaporizes the fuel as it enters the combustion chamber, delivering 15 to 20% better fuel economy over ordinary electronic fuel injection. But you can only get it on a few engines. More new engines will have this system as time goes on.

What about running your car on hydrogen gas? The "HHO Hydrogen Generator" devices that are being peddled on the internet that convert water into hydrogen gas with electricity can't produce enough hydrogen gas to run a lawn mower engine, let alone an automobile engine. The little bit of hydrogen that fizzles out of these things won't make any difference on your mileage either, though the promoters of these mileage saving devices claim dramatic improvements in fuel economy. They claim the hydrogen "supplements" the fuel supply so your engine doesn't need as much gas. It seems logical, but the volume of hydrogen produced by these devices is so small that it has little or no measurable effect on fuel economy.


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.

A more hi-tech version is a fuel economy meter that plugs into the OBD II diagnostic connector on 1996 or newer vehicles. The unit displays instantaneous fuel mileage and cumulative fuel mileage like a trip computer on on a vehicle equipped with this option.


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.

One of the best ways to assure peak performance and fuel economy is to keep your fuel system clean. This can be accomplished by using Top Tier gasoline or fuel system cleaner products that help reduce and/or remove carbon deposits on intake valves, pistons, combustion chambers and throttle bodies.


More and more late model engines are being equipped with Gasoline Direct Injection (GDI). This technology injects gasoline under high pressure directly into the combustion chamber. A conventional electronic fuel injection system sprays fuel under low pressure into the intake port in the cylinder head. GDI allows for leaner fuel mixtures and greater control over air/fuel ratios across a wider range of operating conditions, resulting in 10 to 15 percent better fuel economy and power.

Cylinder deactivation is a technology that provides variable displacement on demand. Cylinder deactivation is used on late model Chrysler Hemi engines in the 300C and other models, as well as certain late model GM V6 and V8 engines. GM calls their cylinder deactivation system "Active Fuel Management." Under low load cruise conditions, the engine management system deactivates four of the eight cylinders in a V8 engine (or three of the cylinders in a V6) to reduce fuel consumption. When the driver steps on the gas to accelerate or pass, the deactivated cylinders are reactivated seamlessly to provide additional power.

Auto makers are going to smaller displacement engines with turbochargers to improve fuel economy. A four cylinder engine obviously uses less fuel than a larger V6 or V8 engine. Adding a turbocharger allows the smaller engine to produce power equivalent to a larger engine when extra power is needed. Examples include Ford Ecoboost and GM Ecotech engines.

Stop-Start Systems on a growing number of late model vehicles 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 this technology can add up to 5 to 15 percent depending on how much stop-and-go city driving you do.

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

The most fuel efficient vehicle are plug-in electric vehicles such as the Tesla, which uses no gasoline at all. Depending on the battery option, a fully charged Tesla 85 has a real world range of around 250 miles, and nearly 300 under ideal conditions. Other electric vehicles such as the Nissan Leaf have a much more limited range (about 60 to 70 miles on a charge).


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 motor oil with a "fuel saving" rating from the American Petroleum Institute (API). Switching from a 5W-30 or 10W-30 motor oil to a lighter 0W-20, 0W-40 or 5W-20 motor oil, and/or switching to a synthetic oil may improve fuel economy a few tenths of a percent (every little bit helps). But don't expect a huge improvement.


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, especially at high speeds during hot weather or with a heavily loaded vehicle.

Increasing the air pressure in your tires can reduce rolling resistance and improve fuel economy (some claim as much as 2 to 3 mpg). The factory recommended inflation for most passenger car tires is 32 to 34 psi (refer to your owners manual or the inflation decal on the door pillar or glovebox). You can safely inflate the tires up to the MAXIMUM limit printed on the sidewall of your tires (typically 38 psi), and can probably go as high as 40 to 42 psi IF you are not driving at speeds above 50 mph, IF you are not traveling long distances, and IF you are not driving during unusually hot weather (over 95 degrees F). Increasing the tire pressure will make your car ride much rougher, so that's the trade-off of adding more air to your tires.

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.

NOTE: Having your tires inflated with nitrogen can be beneficial because nitrogen leaks out of the tires more slowly than ordinary air (which is 78% nitrogen already). Straight nitrogen also contains no humidity (moisture) so tire pressure remains more constant and does increase as dramatically when the tires get hot. This is important if you are running extra pressure in your tires to save gas. Too much pressure increases the risk of tire failure and blowouts, especially when driving at high speeds during hot weather.


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 half 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!


The absolute best way to save gas is to avoid driving altogether. Bum a ride with a friend or neighbor. The best way to save gas is to use somebody else's gas. Make an excuse as you why you can't take your car (such as your car won't start, your car is out of gas, you have a flat tire, the car is in the shop, etc.).

Car pool to work. Use public transportation. Walk (where possible). Ride a bike.

Consolidate shopping trips and plan ahead for the most efficient route (shortest distance or fewest number of stops). Also, run your errands during off-peak driving hours when there is less traffic.

When you do drive, drive as if you had a raw egg under the gas pedal. No jack rabbit starts. Feather the gas pedal gently, accelerate slowly and drive at or below the posted speed limit.

When driving on the highway, find a big truck that is going the speed limit and get in behind it. Don't follow too closely, but maintain a distance of about three or four car lengths behind the truck. There will be enough draft at this distance to significantly reduce the wind resistance your engine has to overcome to push your car down the highway. Following the truck any closer won't reduce the wind resistance that much more , and will greatly increase your risk of read-ending the truck or missing a road sign. And if a cop sees you tailgating too closely, you may get a ticket.

A technique known as "hypermiling" has been coined to denote various driving tactics that can significantly improve your vehicle's fuel economy. Many hypermiling tricks make sense, but others may be dangerous or illegal. Wanna save gas? Some hypermilers say they blow through stop signs (NOT recommended!). Actually, slowing for a stop sign but not stopping completely can save gas. But the cops will give you a ticket if you fail to come to come to a complete halt, even if there is no cross traffic. The law requires a full and complete stop (and that applies to people who are riding bicycles, too!).

Other hypermiling tricks include coasting as much as possible (shifting into neutral, or even shutting your engine off when coasting downhill (which can cause a loss of power steering control and power brake assist!), over-inflating your tires 10 to 15 psi (which can increase the risk of a tire blow-out during hot weather if you go over 50 mph), tailgating large trucks to reduce wind resistance, removing exterior hardware that increases wind drag such as a rooftop rack, antenna and side mirrors, driving as if your car had no brakes (which can really piss off the people following you in heavy traffic). So use common sense if you are considering any of these hypermiling techniques.


Finally, here's a suggestion that can slash your fuel bill 20 percent right now without changing your vehicle, your driving style or buying some silly fuel-saving gadget. Ask your employer to let you work four 10 hour days a week instead of five 8 hour days. You still work 40 hours, but you get to stay home one more day a week saving you the cost of commuting back and forth to work. More and more employers are looking at this as a way to reduce their employees fuel expenses. It doesn't work for every kind of business, but for others it can.

For Fuel Saving Tips from the Car Care Council, Click Here.

Historical Note August 2012: Government Wants Higher Fuel Economy Standards

The Obama administration has reached a formal agreement with automakers and unions to raise the Corporate Average Fuel Economy (CAFE) to a combined city/highway minimum of 54.5 mpg by 2025. Current standards require auto makers to achive 29 mpg for model year 2012, which is up from 24 mpg in years past.

Though 54.5 mpg sounds high today, engineers say it will be possible to achieve significant improvements in fuel economy by using a variety of technologies such as lighter materials (more aluminum and plastic, possibly carbon fiber, etc.), smaller displacement gasoline engines with turbochargers, small turbodiesel engines, hybrids and plug-in electric vehicles. Many 2012 and 2013 model year cars that are available now have highway fuel economy ratings of 40 mpg or higher.

cafe fuel economy graph

Historical Note March 2020: Trump Rolls Back Fuel Economy Standards

In a move that made no sense whatsoever, former President Trump rolled back the Obama era requirements for higher fuel economy standards.

Historical Note April 2022: Biden Restores Obama Era Fuel Economy Standards

The revised CAFE standards apply to model years 2024 and 2026, and mandate an industry-wide fuel economy average of approximately 49 miles per gallon (mpg) for passenger cars and light trucks by model year 2026. The United States is trying to do its part in reducing carbon emissions in the international effort to slow Global Warming and Climate Change.

Historical Note February 2022 Putin's War on Ukraine Causes Gasoline Prices to Spike

Putin's invasion of Ukraine and the corresponding boycott of Russian oil by the United States and some NATO countries has created enormous pain at the pump for all motorists. Gasoline prices that had been around $3 a gallon the year before jumped to over $4.50 a gallon, and as much as $5 in some states. The huge price increases are partly due to a shortage of oil imports but also price gouging by Big Oil. When the international price of oil goes up for any reason, the price of gasoline and diesel fuel at the pump immediately goes up in lock step with spot oil prices. Although it takes MONTHS for the actual increase in cost to work its way through the refining and distribution system, Big Oil always sticks it to the consumer as quickly and as much as possible. And when the global price of oil drops? It takes a LONG time for pump prices to slowly creep back down. What a screw!

More Fuel System Articles:

Fuel Saving Tips from the Car Care Council

Stop-Start Systems

Gasoline Direct Injection

Troubleshooting & Cleaning Fuel Injectors

Fuel Injection Problems

Fuel System Diagnostics: Finding the Best Approach

Gasoline Prices Still High

About Alternative Fuels

E85 Ethanol Alcohol Alternative Fuel

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