Question: Despite rustproofing my 1982 Datsun 310 GX, it has begun to rust through. It seems as if protective coatings don't hold up for long. I've heard that sacrificial anodes are used in Europe to prevent rust. Just what is this method and how good is it?--C.L.
Answer: Rustproofing, which involves spraying sealants into the door and fender cavities, can help limit rust, but it will not prevent rust in cars prone to corrosion.
A recent survey by Runzheimer International, a management consulting firm for automobile and truck fleets, reported that only 22% of commercial fleets use rustproofing. Professional fleet managers cited such factors as improved corrosion warranties by manufacturers as one reason to avoid the expense of rustproofing.
Indeed, automobile manufacturers are using greater amounts of galvanized steel in auto body parts, providing for better drainage from internal cavities and using plastic parts in areas vulnerable to rust.
As for your question about sacrificial anodes, I could not find any automotive use of them in this country. Furthermore, it is unclear whether sacrificial anodes could even be used to prevent corrosion of iron in auto body parts.
Sacrificial anodes are used in marine applications, in which boat propellers can corrode in marinas. Anodes, which are positive electrodes, draw electrical current away from boat propellers. The electrical current originates from battery chargers common in marinas.
Q: I just bought a 1987 Honda Accord LX. When do I need to change the oil, and how often do I need to change it?--R.M.M.
A: The owner's manual recommends changing the oil every 7,500 miles. You should not make the first oil change any sooner, because the manufacturer uses a special oil in the engine to help break it in.
But most auto experts suggest that after the break-in period you should change your oil more frequently. A change every 3,500 to 4,000 miles will probably keep your engine running cleaner and longer.
A recent column describing a problem with static electric shocks in one owner's Toyota Corolla has resulted in an outpouring of ideas from similarly shocked motorists. Such static electric shocks result from synthetic-fabric upholstery used in newer cars, causing a static buildup when a driver or passenger rubs against it.
One woman wrote to suggest that she eliminated a similar problem by spraying her upholstery with a mixture of water and Downy fabric softener. Another woman suggested using spray products that eliminate static cling in clothing.
The most frequently cited suggestion was to hold a key and touch it to a part of the metal frame of the car, thereby discharging the static electricity through the key rather than through a fingertip.
For the Record
In the Your Wheels column (View, June 30) on new motor oil grading, the designations for two oil categories were reversed. The SG category will be the new classification, and the SF category is the existing classification.
Ralph Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.