OIL WEAR SYNTHETIC VS. CONVENTIONAL

THE RECOMMENDED OIL CHANGE INTERVAL FOR NORMAL SERVICE FOR MOST 1980 AND 1981 MODEL YEAR GM VEHICLES (CARS AND LIGHT DUTY TRUCKS) IS 7,500 MILES (12,000 KM) OR 12 MONTHS, WHICHEVER OCCURS FIRST. THE OIL CHANGE INTERVAL FOR SEVERE SERVICE IS 3,000 MILES (5,000 KM) OR 3 MONTHS, WHICHEVER OCCURS FIRST. INTERVALS FOR DIESEL AND TURBOCHARGED ENGINES ARE DIFFERENT; REFER TO THE APPROPRIATE OWNER'S MANUAL OR MAINTENANCE SCHEDULE. GM OIL CHANGE INTERVALS APPLY TO ALL RECOMMENDED QUALITY ENGINE OILS, CONVENTIONAL AND SYNTHETIC. OWNER'S MANUALS FOR THE 1980 MODEL YEAR RECOMMEND THE USE OF SE OR SF ENGINE OIL (SE/CC OR SF/CC FOR DIESEL ENGINES). FOR THE 1981 MODEL YEAR ONLY SF ENGINE OIL WILL BE RECOMMENDED FOR GASOLINE ENGINES (SF/CC, SF/CD, OR SE/CC FOR DIESEL ENGINES). THE QUALITY RATING (SE, SF) OF A PARTICULAR ENGINE OIL IS DETERMINED BY ENGINE DYNAMOMETER TESTS. THESE ENGINE DYNAMOMETER TESTS ARE CALLED SEQUENCE TESTS. SEQUENCE TESTS EVALUATED THE ABILITY OF AN OIL TO RESIST OR PREVENT WEAR, SLUDGE, AND VARNISH DEPOSITS, AND RUST AND CORROSION. THEY ALSO MEASURE THE TENDENCY OF THE OIL TO THICKEN. THE SEQUENCE TESTS HAVE BEEN CAREFULLY DEVELOPED OVER MANY YEARS TO ENSURE THAT RECOMMENDED ENGINE OILS WILL PERFORM SATISFACTORILY IN VEHICLE ENGINES OVER A WIDE RANGE OF CONDITIONS. OIL CHANGE INTERVALS ARE CHOSEN ON THE BASIS OF MANY MILES OF VEHICLE TESTING AND FIELD SERVICE EXPERIENCE. OIL QUALITY, ENGINE DESIGN, TYPE OF OPERATING CONDITIONS, AND OIL CHANGE INTERVAL ALL MUST BE CAREFULLY BALANCED TO ASSURE ENGINE PERFORMANCE AND DURABILITY. SYNTHETIC AND CONVENTIONAL (MINERAL OIL BASE) ENGINE OILS HAVE SOME SIMILARITIES. BOTH OILS ARE BLENDS OF BASE OILS AND ADDITIVES. MOST OF THE ADDITIVES USED IN SYNTHETIC ENGINE OILS ARE EITHER IDENTICAL OR VERY SIMILAR TO THOSE USED IN CONVENTIONAL ENGINE OILS. THE MINERAL OIL USED AS A BASE IN CONVENTIONAL ENGINE OILS IS A MIXTURE OF HYDROCARBONS. THESE HYDROCARBONS (HYDROGEN AND CARBON) ARE OBTAINED FROM CRUDE OIL THROUGH PHYSICAL SEPARATION PROCESSES. THESE PROCESSES INCLUDE DISTILLATION AND SOLVENT EXTRACTION. ON THE OTHER HAND, THE BASE OIL USED IN MOST SYNTHETIC OILS IS OBTAINED BY CHEMICAL PROCESSES INVOLVING MATERIALS PRODUCED FROM CRUDE OIL. THE PERFORMANCE QUALITY OF A FINISHED ENGINE OIL, EITHER CONVENTIONAL OR SYNTHETIC, DEPENDS ON THE CAREFUL SELECTION OF THE BASE OIL AND ADDITIVES. EITHER CONVENTIONAL OR SYNTHETIC ENGINE OILS MAY BE USED, PROVIDING THE OIL IS OF THE RIGHT QUALITY (SF, SF/CC, OR SF/CD) AND THE CORRECT VISCOSITY FOR THE AMBIENT TEMPERATURES ENCOUNTERED (SEE VISCOSITY CHART IN OWNER'S MANUAL), AND IS CHANGED AT THE SPECIFIED OIL CHANGE INTERVAL. IN COMPARISON TO A CONVENTIONAL ENGINE OIL, A SYNTHETIC ENGINE OIL CAN PROVIDE IMPROVED CRANKING AND STARTING CHARACTERISTICS UNDER VERY LOW-TEMPERATURE CONDITIONS (ABOUT -30C (-22F) OR COLDER). HOWEVER, SYNTHETIC ENGINE OILS GENERALLY COST SUBSTANTIALLY MORE (THREE TO FIVE TIMES) THAN CONVENTIONAL ENGINE OILS.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.