Saving gas without pain

By Terry Parkhurst and David Zatz


Planning ahead can make all the difference (and can make driving more engaging). I tend to keep my eye on traffic going as far as I can reasonably see; it saves gas, because I don't slow down as often (and I know what lanes are moving fastest or are clear of traffic), and I have warnings when people ahead are slowing down. Yet, because of advance planning and information, I often end up outrunning people who drive faster, swerve from lane to lane repeatedly, but fail to think ahead; they might tailgate and slam on their brakes repeatedly between flooring their gas pedals, wearing out their engines, clutches, and brake pads, risking accidents, and racking up tickets, but often they don’t really make much better time than someone who also goes faster than traffic, but is clever enough to see further than the one car in front of them.

Part of this is giving yourself some space. Most drivers now leave far less than the recommended one carlength per 10 mph in front of them, opening themselves up for accidents, wearing out their brakes, and slashing their gas mileage. The more space you have in front, the more control you have; you can see further ahead, you can coast to red lights and perhaps not have to stop for them (if they turn green in time), and on the highway you can steady out your speed or accelerate down hills to avoid having to slow down or hitting the gas when going back up again. On the highway, leaving a reasonable amount of space in front (not so much that people are always swerving in front of you) can also make it easier to change lanes rather than slowing down when the need arises, because you'll have time to check out other lanes — and you can do it without making someone else slam on their brakes.

One habit I see in a surprising number of people, including relatively leisurely drivers, is accelerating to the stop sign or traffic light. It’s very common for people, without realizing it, to keep their foot on the gas pedal until they need to actually stop or slow down, and then to switch to the brake. Some people even use both feet. (You can also see this in those cars on the freeway who get very close to the car in front of them, hit their brakes, and then start thinking about moving into the completely empty lanes on either side of them.)

Coasting is your friend, especially when you have a modern car with high gearing; whenever you're hitting the gas despite the need to slow down ahead, even on the highway where you might be coming up on a slower-moving car, any gas you spend maintaining your speed is wasted. It also costs more in brake wear. Simply by planning ahead and coasting when appropriate, I often end up with better gas mileage than driving partners who don’t do these things, despite travelling 10-15 mph faster.

Likewise, if you can change lanes to avoid hitting your brakes, without getting in anyone’s way, do it. (One thing that drives me crazy, by the way, is people who change lanes without checking their mirrors first and waiting for oncoming traffic to go by. Yes, sometimes those brakes have to be used.) I'm always having to stop because some guy in front can’t figure out how to get by the car that’s making a dreadfully slow turn. Which brings up another issue - faster turns can save gas, because you don't have to slow down so much and then make it up with the gas pedal. I'm not asking you to whip around turns so fast you can't see what's ahead, or so that a little bit of road debris will send you out of control, but there's also no reason to slow down the dump truck that's making the same turn... okay, maybe you don’t drive that way, but a lot of people do.

If the car is going to idle longer than 30 seconds, you save gas by turning the engine off and then, restarting it, when ready to go. So if you’re stuck at a stoplight, a train crossing, waiting in a parking lot, in the midst of freeway congestion or even at a drive-through bank, make it a point to turn the engine off, when you can.

Gasoline engines like to be run at a constant speed - rpm, if you have a tachometer. Smooth driving saves gasoline. Flooring the gas pedal puts most cars into an “open loop” mode where sensors are excluded, and a richer fuel mixture may be used, wasting fuel at an unusually high rate; gentle driving saves fuel. As one writer put it, a single jackrabbit start can use as much fuel as a considerable period of spirited driving. Don’t accelerate so slowly you drive everyone else crazy, but if you’re always the first out of the light and ahead of the guy next to you by half a block before the guy behind you has started moving, you’re probably driving your gas mileage down unnecessarily.

Try to keep your vehicle in its ideal range, whenever possible. The ideal fuel economy speed for each car depends on gearing, aerodynamics, and engine characteristics, but it's often achieved between 1,500 and 3,000 rpm in the highest gear. Going faster than 55 mph in most cars results in increasingly lower mileage, as wind drag increases and gearing stops being optimal; this may especially be true for cars designed to get good pre-2008 EPA ratings rather than good real-world mileage. There are, of course, exceptions; for example, the Neon was given a fairly high top gear and low wind drag, so the difference between 55 and 65 may be nominal.

As Red Green would say, we’re all in this together. If I save gas, demand falls, and prices go down. So try to help other people, too. Don’t run through stop signs like they don’t exist (a common practice in some parts, and very uncommon in others); don’t stop for someone who doesn’t have the right of way, making everyone behind you stop; don’t force yourself in, impatiently, without regard to that line of cars, all of whose drivers will have to hit the brakes, and don’t change langes with no regard for that guy who’s coming up fast in the passing lane. When you make a left turn, be in the left part of the road so people can drive around you. When making a right turn, don’t swing over to the left first. I can’t believe people still do that in this day and age, when just about every car can make just about any turn. It’s dangerous, inconsiderate, and wasteful.

Again, as Red would say: I’m pulling for you. We’re all in this together.*

Car maintenance

Al Runte, noted historian and writer, had a problem when he needed to go to Montana to deliver a series of lectures on trains and national parks: how to get around in the most efficient way possible?

Runte decided to leave his 1996 Ford Taurus at home. Instead he rented a 2008 Buick Lucerne, equipped with a V6 and four-speed automatic. On the open roads of Big Sky country he found that at 70 mph, hour he could achieve 27 miles-per-gallon, even with the windows up and the air-conditioning on.

His key to better mileage is over-inflating the tires a bit. “I inflate all the tires to 35 pounds per square inch, when they’re cold,” said Runte. “And then, they’ll get to between 38 to 40 psi then, when they get hot.”

Keeping your tires inflated to at least manufacturer’s recommendations are vitally important to good gas mileage. Underinflated tires can reduce fuel economy by 2% per psi. That means if your tires pressure is 27 pounds per square inch (psi) when it should be 32 psi, you may have reduced your gas mileage by 10%.

Over-inflating the tires may increase wear in the center of the tire, and tends to stiffen the ride; overinflating can also increases the risk of blowouts. Never inflate the tires past the number printed on the sidewall.

When gas stabilized in the 1980s, people began to forget an easy way to save gas: don’t let the engine idle too long. EPA tests have shown that it is more economical to turn the engine off rather than let it idle, if the idling time is going to exceed 30 seconds.

“Most people focus only on the price of gas, but there are some low-cost parts that consumers can replace, that can save them save them substantially,” said NAPA’s (National Auto Parts Association) Technician of the Year (2008).

Vintage cars

While it might not be as important with modern engines to change oil as frequently as in the vintage days – many modern engines boast of being able to go to 10,000 miles before the first oil change – using a good engine oil, or synthetic, in combination with changing oil filters themselves, with the oil, is going to help save fuel. However, changing the oil of any car, even one with a modern engine, is going to vary depending on duty cycle. (The American Petroleum Institute defines severe service operations as those which include trips that are less than 10 miles; driving in dust or sand; cold weather that prevents full engine warm up; idling for extended periods; stop-and-go driving; or pulling trailers or other heavy loads.)

On any car, spark plugs can be critical. A Hagerty’s article covering gas mileage pointed to one test, where a car capable of 26 mpg got just 21 mpg with the plugs gapped .02” too tightly, and 19 mpg when the plugs were gapped .02” too widely. The same article pointed to the advantages of higher-quality parts for all ignition components, including the cap, points, and rotor; and to checking the fuel pump for decay. Having experienced a leaky fuel pump (ours actually sprayed fuel wildly), we can say that this is one area to be checked frequently on vintage cars.

In terms of fuel economy, one of the most critical adjustments on older cars is the air-to-fuel ratio (the amount of air burned for each part of fuel). The air/fuel ratio should be set on what is called “the lean side” to obtain best mileage. Modern cars, with full computer control, automatically keep the ratio correct; if you have a carburetor or tuneable fuel injection (again, this will not be the case on modern cars), the most effective way to set this ratio is by using an exhaust gas analyzer, available at most mechanics' shops. Rick Ehrenberg of Mopar Action also described a way to create your own by using a spare oxygen sensor and some electrical wizardy. Carburetors that have been running too rich, when leaned out, can see improvements in fuel economy of five miles per gallon. What’s more, the idle speed matters: Hagerty claimed a 2% gas mileage decrease for every 50 rpm of extra idle speed.

Finally, older cars (without oxygen sensors to adjust the fuel mixture as needed) are susceptible to clogged air filters enriching the fuel mixture, making it especially important to replace them. Some “interim” cars made during the years when fuel injection was phased in may have small openings for the air to flow through the filter, so that the engine is starved for air under high load when the filter is even mildly clogged.

Owners may have luck with advancing the timing, a little at a time, and backing off when the engine knocks. This practice can be a little risky, since there is a risk of detonation, but numerous vintage car owners have been known to do it. One owner of a pristine, daily-driver Plymouth Valiant who routinely gets over 20 mpg around town suggested that owners could push timing five degrees forward before knocking, even under load; the advantage is both stronger responsiveness and a sizeable increase in gas mileage. Other tricks for carbureted cars include lowering the idle speed a little, so that the car can still run smoothly and doesn't hesitate, but loses a little gas; the main losses here are in air conditioning power and charging system capabilities at idle.

Modern cars

With fuel-injected cars, you might need to replace the injectors or simply replace the oxygen sensors; though usually the engine computer will tell you when the oxygen sensor is bad (since there are two, one to check the other), there are times when the computer might be fooled, especially if both sensors have been contaminated. Sensors typically cost over $40, but are easy to replace on most cars if you buy an inexpensive oxygen sensor wrench (which has an opening for the wire). As for fuel injectors, they may need to be cleaned if they no longer atomize the fuel properly, but drip or spray large droplets; any well equipped shop can unscrew them and test their spray pattern, and cleaning is often possible.

All cars

To keep fuel economy optimum, air filters should be inspected and replaced annually, if they are clogged with dirt, dust or bugs (on many cars you will have to take the air filter off and flip it over to see the “dirty” side). Once clogged, air filters can create a rich air-to-fuel mixture, especially at wide-open throttle, which wastes gas and also causes the engine to lose power.

Ultimately, the surging price of petroleum – with gas and diesel following suit – might mean reconsidering options not used for decades. Machinist Mark Pringle has a late model Chevrolet half-ton pick-up truck, but now he commutes to work in a pristine 1966 Volkswagen Beetle he recently bought off eBay. Gas mileage isn’t in the league of larger, newer vehicles like the Toyota Corolla, but in mostly freeway driving he’s hit 30 mpg. His vintage Beetle is mostly stock, but has a 1974 alternator (instead of its original primitive generator) and radial tires. He’s considered buying NOS (new old stock) bias-ply tires from Coker Tire and maybe sizing them to 15-inch radius. Then, he’d sell the radials at a swap meet or on-line. “I figure I’d lose some handling,” said Pringle. “But I’d gain some additional mileage, since I’d have lower rolling resistance.”

Sometimes, there are few losses from car-changing adjustments. If your car was made with different wheel sizes, going down in wheel size can reduce unspring weight and rolling resistance; remember, those mighty Hemi-powered muscle cars back in the 1960s had 15-inch rims! Going down a single size, if the +1/-1 system is used, while upgrading to a higher quality tire than OEM could actually result in a net gain in cornering, while cutting gas mileage and possibly improving snow traversal. (The +1/-1 system adjusts the size and profile of the tires to maintain the same diameter, so you don’t throw off your speedometer, odometer, and, most important, your engine computer, while swapping tires.) What’s more, you can actually save enough money by buying the higher-profile, smaller-diameter tires to pay for new wheels... especially if you find a buyer for the old ones - and you can make money if you swap with someone who wants bigger wheels! Just make sure you investigate the conditions for your car before doing this. Sometimes, higher end models have bigger wheels and tires for a reason; on the PT Cruiser GT, for example, the big wheels and low-profile tires are actually needed to prevent wheelspin from the turbocharged engine.

One often overlooked candidate for saving gas without pain is weight. Yes, there are the wheels, but there are lots of other things you carry around. Seats are generally fairly light these days, and have been since the 70s; but what else are you carrying? Are there two spare tires? Jugs of water? Steel I-beams? (Yes, I know someone who carried around steel I-beams in his 2.2-liter, four-cylinder 1980s Dodge Caravan for years... and wondered why he had transmission problems after crossing 100,000 miles.) Empty out that trunk... keeping, of course, the compact spare and the jack, first aid kit, and whatever you actually need.

Then look around the outside of the car. Are the mirrors correct for the car or aftermarket addons that increase wind drag? Do you keep the car waxed (a good polymer wax lasts six months)? Do you have a cute ball on the antenna? Are the doors properly lined up and body panels all where they’re supposed to be? Did you scrape off the little black spoiler under the front bumper and never got around to putting it back on? All these things can increase your wind drag and hurt highway mileage.

If you’re in the market for a new car, consider the type of driving you do and your real needs. If you need to take something big home from the hardware store every few months, you can borrow or rent a pickup or pay for delivery, and the rest of the year reap the benefits of a smaller vehicle. If you need seating for seven but just can't bear to be seen in a minivan, spring for a shrink. Actually try one o’ them four-bangers or manual-transmission cars (assuming you know how to drive one, but haven’t done it in a long time) before writing them off. Forget about image and style and at least look at the car you need instead of the car you want, and you might be surprised. Sometimes you don’t really give up a lot. Driving the various cars and crossovers and SUVs and trucks offered by various makers, I’m sometimes reminded of the late 1980s, when you could get a four-cylinder, front-wheel-drive Plymouth that was bigger inside, faster, and more comfortable than the much larger V8, rear-wheel-drive Plymouth sold alongside it (mainly for the benefit of the police and taxi departments, who needed something that could truly take a pounding and was cheap to fix after an accident.)

If you spend a lot of time sitting in traffic or at lights, a hybrid will probably pay off; if you spend a lot of time cruising on the highway, think diesel, four-cylinder, or, at least, cylinder deactivation. But be reasonable - there are lots of cars where a four cylinder isn't much more efficient than a V6, and a few where the V8 actually seems to do better in the real world than a V6. Toyota’s automatic transmissions generally get around the same mileage as their stick-shifts, though there’s a performance cost. And then there’s the best choice, if you can do it — waiting. Gas mileage will increase over the next few years as manufacturers re-gear, strip weight, and use new technologies. Chrysler alone is set to bring out a bunch of new V6 engines with variable cam timing, automated manual transmissions, and engines that shut off when you stop at a traffic light, without having to carry heavy hybrid batteries and motors. Not only that, but buying a new car is very expensive in both money and energy — it takes a long time to recoup either one.

There are a lot of things you can do to increase your gas mileage and cut your costs; but of course, the most effective is not to drive. Combine trips, consider whether this trip is really necessary, and try to carpool or take mass transit (if it exists), and your gas bill will fall farther, faster. Four people driving in a single Suburban pay less for gas than four people each driving carefully in well-optimized four-cylinder mid-size sedans.

Other activities

Gasoline isn’t the only thing that’s going up; your taxes are rising every year as garbage disposal costs climb, your electric bill is going up, and if you have gas or oil, that’s going up too. You can cut quite a bit out of all of those if you just think about your habits for a while. It doesn’t take massive expenses or draconian cuts to save a lot of fuel and a lot of money; sometimes it’s as simple as looking at the Energy Star ratings before buying a new appliances, spending a few dollars on insulation, shutting off some lights or closing the computer overnight, using the Energy Star features on your computer and monitor, getting compact fluourescent replacement bulbs (from a reputable supplier, like Phillips, that makes them well and with relatively little mercury), and lowering the shades and closing the windows in the morning to keep the house or apartment naturally cool. Some of our habits, as Americans, are truly odd. The most popular water heaters are the least efficient - and the more efficient models only cost a little more, and last longer, so that even if you didn't save on the energy you'd save on the lifespan. Plumbers put in high efficiency boilers with piping that makes them more wasteful than the massively oversized pre-Depression units. Computers are made with no regard to energy consumption though they run 24/7; and people never shut theirs off, even if they're only used for ten minutes a day. Some people even use full 300 watt computer systems just as file servers, ignoring options like NAS drives. And then there are municipal services, like garbage collection, whose costs are somewhat hidden, so that people think nothing of using disposable, nonbiodegradable dishes or buying disposable-everything; though they come back in the form of tax increases (or, for apartment tenants, rent increases).

This country used to have a strong ethic of frugality. Maybe that came from the Puritans, maybe it came from the constant cycle of recessions and depressions that ended when FDR brought Federal control to the banks; but it seems to have largely vanished, not only among native-born Americans, but among immigrants as well. As one observer on the Allpar weblogs noted, being frugal is accidental environmentalism; and saving money by cutting your energy costs can help reduce the impact of global warming, if scientists’ theories are correct. But more to the point, it saves money.

* I know he was referring to growing old, not saving gas.