Is power steering electronically controlled?

Dear Bob: Is power steering electronically controlled in any way? If not, is it totally mechanically controlled by the setting for fluid pressure?

In either case, does the pressure while adjusting to the degree of turn also affect the play in the steering wheel?

Thank you.

— M.G., Westwood, Kan.

A: There have been a number of vehicles that have employed electronic assist in their power-steering systems, but these are the exceptions rather than the rule.

Most vehicles today are equipped with power-steering systems that are hydraulic-dependent, using fluid pressure to assist with the steering chores.

Many vehicles have variable-assist power steering, in which the amount of assist offered by the system varies depending on driving conditions. More assist is provided in tight situations such as parking, less when cruising on the highway, where little effort is needed to control the steering wheel. For instance, the Lexus LS 430 employs what Lexus terms “vehicle speed-sensing progressive power rack and pinion steering.”

Excessive play in the steering wheel is usually caused by the wearing-out of mechanical parts or by the need for a steering-column adjustment, rather than by the hydraulic pressure in the power-steering system.

Dear Bob: The increasing problem of air pollution from vehicular travel in the U.S.A. precipitates this question.

Do the existing air filters associated with the cooling or heating systems in the average vehicle help clean the air? How effective are they?

I have never heard this issue addressed.

Yours truly,

— Dr. G.W.B., via e-mail

A: Many newer vehicles offer cabin-filtration systems as standard equipment or options. Air passed through the HVAC — heating, ventilation and air conditioning — systems is filtered before it enters those systems, and is later emitted from vents in the dash and other areas.

Many manufacturers claim that their systems can filter out particles of dust, allergens, spores and other pollutants as small as one micron, leaving the interior a more environmentally healthy place to be. A micron — one millionth of a meter — is pretty effective, in my opinion.

The air drawn into the HVAC system, and later filtered before being discharged into the cabin, comes from outside the vehicle. So I guess, in a roundabout way, these filters also clean the outside air.

In the overall context of our polluted air, however, the impact of a car’s filters is minimal. It’s not nearly enough to compensate for the air pollution generated by the car itself, let alone reduce pollution overall.

Dear Bob: I own a 2002 Chevy Malibu. How often should I change the power-steering fluid? I can find no information on this anywhere.

— I., via e-mail

A: Most car manufacturers don’t give a change interval for power-steering fluid, so it can often go unnoticed and unchanged for tens of thousands of miles.

My suggestion is to change the fluid as often as the manufacturer recommends that the transmission fluid be changed, usually somewhere between 30,000 miles and 50,000 miles. The fluid can be siphoned out of the fluid reservoir and new fluid put in. Many quick-lubes now offer this service for a reasonable fee.

Don’t be concerned about the small amount left in other parts of the power-steering system, because it will be flushed and combined with the new fluid.

AMERICAN DRIVERS FIGHT BACK

Here’s a tip that will help you get better gas mileage while fighting terrorism and cutting our nation’s dependence on Mideastern oil:

Too many drivers have the habit of revving their engines before shutting them off. They erroneously think that an extra pump or two on the accelerator pedal will circulate oil throughout the engine and thus give better protection when the engine is off.

Actually, exactly the opposite is true: Besides wasting gasoline and irritating your neighbors, pumping the accelerator while idling causes a surge of raw gas to flood the cylinders. Much of this gasoline, because it doesn’t have time to be ignited, ends up diluting the oil and washing away vital cylinder-oil coatings.

This makes the next start a truly dry one instead of a nice, lubricated one — exactly the opposite of what many vroomers think. This practice accomplishes nothing, except turning heads if you have a loud muffler and/or a big ego.

So don’t vroom-vroom before shutting down the engine — you’ll only waste gasoline and accelerate engine wear. Simply turning off the ignition will do fine, thank you.