Additives, not always listed as part of the oil recipe, are also a factor to take into account. Listed below are some of the more common additives found in motor oil:
- Detergents: Help remove some deposits, but mostly inhibit the formation of high-temperature deposits, rust and corrosion.
- Antiwear additives: When the lubricating film created by the oil breaks down, the antiwear additives protect the metal surfaces.
- Viscosity-index improvers: Lessens the oil's tendency to thin with increasing temperature.
- Foam inhibitors: The crankshaft rotating through the oil in the pan causes foaming. Foamy oil does not lubricate as well as full-liquid oil. The inhibitors disperse the foam.
- Friction modifiers: These reduce engine friction and (technically) improve mileage.
While additives are an excellent addition to car and truck oil, they have to be balanced against many factors and sometimes too much can be a detriment rather than an advantage.
For example, sulphur compounds provide antiwear properties, but they can also reduce fuel economy and affect catalytic converter operation. Adding too much detergent could affect the antiwear balance of the oil. Friction-reducing additives also may have ingredients that could affect the catalytic converter.
Additives represent anywhere from 5 to 30 percent of a given quantity of oil. How they function within the oil is dependent on the base oil, the type of oil, viscosity, and a host of other factors. Every oil has a recipe, some will work well in an engine, some will not.
Among the best ways to find the right motor oil for your car or truck is to use the manufacturer's base recommendations, do a little research on the subject and then make the call. Also keep in mind that frequent oil changes, as well as frequent filter changes, play a key role in keeping an engine running for the long haul.
For more information about choosing the right oil for your car or truck and other related topics, follow the links on the next page.