Question: I've heard that oil companies have now introduced a motor oil that replaces the old, SG-rated type. What is the new oil and should I use it in my 3-year-old car?--M.S.
Answer: Major manufacturers are just now shipping a new oil with better lubricating properties that will improve engine protection. The new oil bears the SF rating, replacing the old SG rating.
The higher-rated oil certainly can be used in older cars. These ratings, which are usually stamped on the top of the oil can, are provided by the American Petroleum Institute and represent an independent approval of the product's quality.
The new SF oil will contain 40% to 60% more additives than current SG oil, according to Norm Hudecki, Valvoline oil expert. Today's SG multigrade oil is about 20% additive and 80% petroleum, and SG single-grade oils are typically 8% additive and 92% petroleum.
For the Record
Los Angeles Times Thursday July 7, 1988 Home Edition View Part 5 Page 7 Column 4 You Desk 1 inches; 31 words Type of Material: Correction
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.
Ford will recommend that owners of its 1989 cars use the new SF oils. General Motors will recommend SG but will tell owners they may switch to SF as it becomes available.
The new SF oils will be a "premium-priced product," meaning they're going to cost a lot more. But they will provide better sludge protection and should provide better engine-wear protection.
New oils have been a real boon to motorists and have made a big difference in engine longevity. With proper care and frequent oil changes, a well-made auto engine, according to Hudecki, should have more than 150,000 miles of life. "Engines are lasting longer," he said. Q: My 1985 Oldsmobile Cutlass has been consistently overheating on warm days. I have had the fluid level checked, the cooling system flushed, the water pump checked and the thermostat changed. But it is still running hot, though not quite boiling over. What could be the problem?--J.E.
A: There are several potential causes of the problem you describe. One simple problem may be that you have a defective radiator cap, an often overlooked cause of engine overheating. The radiator cap keeps the cooling system pressurized, generally at 14 to 17 pounds per square inch.
If the pressure drops, the boiling point of the coolant drops and it begins to boil off. The loss of just 1 pound per square inch of pressure results in a 3-degree drop in the boiling point. A radiator cap fails because the rubber seal deteriorates or the pressure-release valve becomes worn. This is about the least expensive and most overlooked problem in cooling systems.
A second cause of your problem could be a partially clogged radiator. Often a simple flush will not sufficiently clean out the dirt that coats the radiator and coolant passages inside the engine. A chemical flush, accompanied by a back-flush, is a more effective procedure.
Finally, the engine itself could be generating higher-than-normal temperatures that exceed the capacity of the cooling system. The causes of excessive engine heat could be such things as an overly lean air-fuel mixture from the carburetor or insufficient engine lubrication.