Q My 2002 Acura RSX has an oil-consumption problem that began two years ago at less than 50,000 miles. It suddenly started using three quarts of oil in a 3,000-mile interval without any drips or smoke. Two oil-consumption tests at the dealer showed sporadic usage, ranging from almost no consumption in 500 miles to more than a quart in 500 miles. The average was a little less than one quart per 1,000 miles.

I've paid for a compression test, valve inspection and adjustment, a top engine clean, and synthetic and regular oil changes with Sea Foam. Those haven't changed the consumption in the last 22,000 miles.

The dealership could only suggest a tear-down of the motor but wasn't sure if that would turn up anything. They flatly deny that a failing PCV valve could behave this way. Corporate Acura says this consumption is "normal" because it averages less than three quarts per 3,000 miles.

A In my experience, oil consumption caused by mechanical wear is relatively consistent. Erratic oil consumption, on the other hand, can be caused by high operating temperatures that thin the oil to the point consumption increases, or some type of blockage in the crankcase ventilation system that allows oil to be forced into the combustion chambers. The fact that the pattern of oil use hasn't changed in the past 22,000 miles points away from a "wear and tear" cause.

Despite what the dealership says, replace the Positive Crankcase Ventilation (PCV) valve, and check the entire PCV system for any leak or blockage. Intermittent PCV action can cause erratic oil consumption.

A more unusual cause for erratic oil consumption might be oil that is trapped on top of the cylinder head and doesn't drain back into the oil pan fast enough. This would progressively reduce the volume of oil in the pan, which would cause oil temperatures to rise, perhaps leading to higher consumption. This scenario would be most likely to occur during periods of continuous higher-rpm operation where a higher volume of oil would be pumped up to the cam/rocker/valve area on top of the cylinder head. To test for this, you could try quickly checking the oil level after a solid half-hour of highway driving. If it's low, but returns to normal once the engine cools, this might be the issue.

One final thought. Acura calls for 5W-20 motor oil. I'd suggest trying a 5W-50 synthetic such as Castrol Syntec or Quaker State "Q." Typically, the use of synthetic oil will lower the oil temperature and maintain higher viscosity at full operating temperature, reducing oil consumption.

Q There's been a lot of talk about the value of maintaining good tire pressure as one factor in maximum gasoline efficiency. Do you agree this is important, and is there a kind of tire-pressure gauge you recommend? I am thinking of getting some for birthday presents.

A Yes, I do -- and wonderful idea! Proper tire pressure -- typically near 35 pounds per square inch for passenger cars -- minimizes rolling resistance, reducing the amount of power required to roll the tire. And that means better fuel mileage.

But that's only one benefit from proper tire pressure. Longer tire life, better ride quality, better braking action and quicker steering response are just as important, particularly in terms of driving safety.

Stop by virtually any auto parts store and pick up a handful of battery-operated digital tire gauges for less than 10 bucks each.