fewer and lighter moving parts. Such engines can run faster (i.e., at higher rpms) without engine damage, so it's possible to achieve the same horsepower with a smaller engine and save fuel. Overhead camshafts allow for optimal placement of intake and exhaust ports, too, which

improves efficiency. And less engine friction is created so that less energy is lost this way.

As fuel costs rose during the 1970s and early '80s, automakers began using this technology more often. Doing so has helped fuel economy, but it may not involve as much fuel saving as has been estimated. In fact, the benefits of overhead cam, multivalve cylinder heads, and other engine changes are so closely related that sometimes they are counted twice.

• Installing variable valve control mechanisms can provide an estimated 3 to 5 percent improvement in fuel economy by maintaining better air and fuel flow into the engine. The valves on most of today's cars are opened and closed at fixed intervals, relative to the position of the crankshaft, for all engine operating levels. Engines run more smoothly and efficiently, though, when valve openings and closings are varied according to the engine's temperature, load, speed, and other conditions.

Estimates of the fuel economy benefit associated with variable valve control differ widely because the term "valve control" actually includes a number of different technologies that affect valve timing, lift, etc. Depending on which technology is used - and whether it's programmed toward improving fuel economy or improving performance - a wide range of benefits may be estimated. These yield, on average, an approximate 4 percent improvement in miles per gallon.

• Applying advanced friction reducing technologies can provide an estimated 5 percent improvement in fuel economy by cutting down on the energy that's lost to

friction. Such technologies include those designed to reduce the number of engine parts that contact one another. They also include technologies designed to make engine parts fit better at a wider range of operating temperatures. Pistons, for example, may be redesigned to reduce distortion and, hence, friction from contact with the cylinder wall.

Rolling along a surface inherently involves less friction than sliding, so another example of advanced friction reducing technology is a valve lift mechanism that rolls instead of slides along the camshaft. Rolling lifters are a relatively new automobile production technology, but most other known friction reducing technologies are already in place.

• Using fuel injection can provide an estimated 3 to 4 percent improvement in fuel economy, depending on the type of injection system that's used. Virtually all new cars have fuel injection instead of carburetors - a fuel economy as well as performance benefit because injection provides the engine with a fuel-to-air ratio that's closer to optimum for a wider range of engine conditions. Throttle-body fuel injection systems do a good job of optimizing fuel mix, and more advanced multipoint systems can do an even better job.

• Putting more gears on automatic transmissions can provide an estimated 3 percent improvement in fuel economy (four-speed) plus another 2 percent improvement (five-speed), compared with three-speed automatics because, simply stated, the more gears an automobile has the more time it can be operated at or near its optimum efficiency.

sions are overstated because they assume the additional gear will be used exclusively toward improving fuel economy without regard to performance - an unlikely assumption. Most automobiles are geared for a compromise between the two, and the Institute's 3 percent improvement estimate for a four-speed automatic assumes such a compromise

• Equipping cars with continuously variable automatic transmissions proba bly doesn't result in any fuel saving, compared with manual five-speeds.

In theory at least, an infinite number of gears means that a car can always be operated in the optimum gear. Based on this principle, the continuously variable transmission made its debut in a 1903 Oldsmobile model. But such transmissions haven't been used in many cars over the years because, even today, only those cars with very small engines (90 horsepower or smaller) can accommodate such a technology

Continuously variable transmissions offer virtually no fuel benefit compared with a manual transmission. Subaru's Justy equipped with a five-speed manual gets an average of 34.5 miles per gallon (city and highway), according to Environmental Protection Agency ratings, compared with 34 7 miles per gallon for the same car with a continuously variable automatic transmission.

Any benefit from continuously variable transmissions has to be realized in stopand-go urban traffic, where a great deal of shifting is required. On the highway, continuously variable transmissions offer little or no fuel saving at all.

• Adding a lockup mechanism to the torque converter on automatic transmis sions can provide an estimated 3 percent improvement in a car's fuel economy by eliminating the fluid energy losses associated with transmitting power from the engine to the transmission through the torque converter About half of all new cars mainly midsize and large cars have torque converter lockups.

• Equipping cars with electronic gearshift controls can provide an estimated 0.5 percent improvement in fuel economy. With an automatic transmission, the gears are shifted according to speed, engine rpms, and other factors. Electronic controls measure these factors and then shift the gears for optimum operation either optimum performance and accelera tion or optimum fuel economy

The reason the fuel economy benefit from this technology is so slight is that the hydraulic gearshift controls on most cars today are so well developed that a new kind of control would offer only minimal improvement. Whats really pushing automakers toward using electronic controls isn't fuel economy alone - it's the fact that such controls allow drivers the treedom to switch the transmission between optimum fuel economy and optimum performance. For example, drivers with this feature can choose to switch to lower gearing on a hilly terrain, even though it may cost extra fuel.

• Changing to front wheel drive can improve fuel economy by up to 2 percent, compared with rear wheel drive, because front-wheel-drive cars are lighter. However, the gains in fuel economy don't even approach the 10 percent estimate mentioned in a US. Department of Energy report. This is primarily because the high estimate is based on comparisons between newly de signed front-wheel-drive cars and older rear-wheel-drive cars of the 1970s -- an invalid comparison because substantial weight reductions unrelated to the switch from rear to front wheel drive occurred at the same time.

Comparing cars for which the only substantial change is a shift from front to rear wheel drive produces much smaller weight and fuel savings.

Going to front wheel drive has allowed automakers to mount engines transversely. Most have done so, usually at the same time as substantial downsizing. So it's not surprising that many estimates of fuel saving from front wheel drive are really from

the weight reductions associated with the smaller wheelbases of downsized cars

It's important too, that R2 percent of all 1989 cars are front-wheel-drive mors This means most of the benefit assox LT with this technology may aiready have been realized

• Adding a two-speed gearbox for power accessones can provide a smal, inprovement in fuel economy In todays cars, engine power operates accessories like power steering at whatever speed es gine rpm level) the car happens to be op erating. This means that at higher roms accessones are wastefully overpowered Its a problem that could be reduced by adding a two-speed gearbox specifically to power accessories.

Proponents of tougher fuel economy standards say the kinds of technologies discussed above can help automakers meet new requirements without further car downsizing Senator Howard M. Metzenbaum of Ohio for example said pro posed requirements can be accompashed strictly by deploying familiar, off-the-shell technologies throughout the fleet" He as er added. "In no other area of energy of environmental policy can we achieve so much gain with so little pain.

But, without downsizing, it's not this simple. Some of the technologies that en hance fuel economy aren't ready to imple ment fully. Others are already in wide use. Front wheel drive, for example, is a feature on so many cars already that it's questionable whether it offers much potential for further fuel saving

Some proponents of tougher standards have overlooked the fact that several technologies are related, so their benefits shouldn't be added together Plus, these estimated benefits don't necessarily fully account for inherent conflicts between fuel economy, performance, and driveability

An even more basic problem with est mated fuel economy benefits from various technologies is that fuel economy isn't a function of manufacturing decisions alone It involves a complicated mix of factors in

cluding especially consumer preference.

In today's car market, consumers are purchasing energy consuming instead of energy saving features at an escalating rate. More than 85 percent of all the new cars Ford sells, for example, are equipped with automatic transmissions. Nearly 95 percent have air conditioners. These are both features that decrease fuel economy, as do other popular features such as power windows, door locks, and seats.

Another growing trend is

for cars that accelerate faster-important to the fuel economy debate because a 10 percent increase in 0-60 mph acceleration time can produce a 5 percent decrease in fuel economy Engine horsepower to automobile weight ratios have increased in ev

ery model year since
1982, costing fuel as
well as occupant
deaths. Institute re-
search on death rates for
103 car series (1985-87 mod-
els) found high-performance
cars accounting for four of the
five with the highest death rates.

By the same token, consumers
aren't purchasing cars with many
of the characteristics that enhance
fuel economy. Midsize cars are of
ten marketed with either four- or
six-cylinder engines, for example,
but the more fuel efficient four-
cylinder versions often don't sell as
well as the cars with the larger en-
gines. Diesel engines are highly fuel
efficient, but they accounted for less
than 0.1 percent of 1989 model new
car sales, down from a high of 6 per-
cent in the 1981 model year.

On the other hand, there are fuel-saving technologies on the horizon that mo torists might accept. General Motors and

Government regulatory programs tend to be administered separately, often without close coordination among agencies. and fuel economy standards are no exception At the same time Congress was enacting the Energy Policy and Conservation Act of 1975, for example, it was encouraging gasoline consumption by imposing strict price regulation on crude oil and refined products.

Fuel economy standards are still at odds, in many cases, with passenger car safety standards. Not only have the former pushed some automakers to produce smaller, less safe cars, but also the safety features mandated by federal standards have added weight to cars, thus reducing fuel economy. For example:

• The addition of lap/shoulder belts in rear seats adds 1 to 4 pounds to the weight of a midsize passenger sedan.

• Head restraints, which are designed to reduce injuries in rear-end collisions, add from 4 to about 10 pounds.

million cars are expected to be sold with full front-seat air bags. Theres no doubt lives are already being saved. This is, in fact, one of the most important motor vehicle safety advances ever. But, like many other safety features, air bags add weight - about 21 pounds per car, according to the U.S. Department of Transportation.

• High center-mounted brake lights, which add about a pound to the weight of a car and use energy, have been required equipment since the 1986 model year be cause they help drivers avoid crashes and lessen injury severity in the crashes that occur. These lights have been proven to reduce crashes but, at the same time, they have an adverse effect on fuel economy.

Another example involves special running lights wired to come on automatically when the engine is turned on. Required in Canada, Norway, and Sweden. daytime running lights have been shown to reduce crashes between cars during daylight hours. But they

arent required in the United States. When the U.S. Department of Transportation considered issuing a rule to permit them General Motors said it didn't expect to introduce daytime running lights because of the fuel economy penalty Such penalty which amounts to approximately 0 25 miles per gallon, might delay this important safety technology

Now before the US. Department of Transportation is rulemaking to upgrade side impact protection. If implemented the tougher standard almost certainly will increase the weight of new cars, thus decreasing fuel economy.

The direct weight gain associated with a tougher side impact protection standard could reach about 50 pounds per car, according to regulatory impact analyses so the fuel economy implications might be considerable. Yet such improvement is definitely needed, from a safety standpoint, to protect car occupants in side impacts.