By Pat Lannone
All motor oils, conventional, synthetic blends and fully synthetic contain various additives to make it perform better, motor oils also contain additives in different values which help prevent engine wear.
Oil changing with oil filter replacement is a very important car maintenance item. It is advisable to choose the one that is correct for the type of engine in your car by consulting the manufacturer’s instruction manual. Using the wrong oil can cause damage to your engine and could void the warranty, if it is a new or rebuilt engine. The best guide to making the right choice is to ensure the American Petroleum Institute Certified (API) Starburst stamp is visible on the motor oil to be used. The API donut also helps you by indicating the performance of the motor oil, and its viscosity at different temperature levels or in other words, the Society of Automotive Engineers (SAE) rating. Today’s performance oils will also conserve fuel.
Understanding viscosity
When choosing motor oil for your car, the most important consideration to keep in mind is its viscosity or the thickness of the motor oil. Motor oils that are too thick will not flow freely and cannot move through all the moving parts of your engine. They cannot effectively protect your engine from friction, contaminants and overheating. However, if the motor oil is too thin, it will not be able to coat the engine properly and is also ineffective.
Ambient temperatures, the temperature which surrounds an object, can also affect the thickness and fluidity. Motor oils tend to thicken at lower temperatures and thin when the temperature rises. As a result, starting up the engine in winter can be more difficult and also consumes more fuel to reach the optimum temperature for combustion. Accordingly, manufacturers include additives in the motor oil so that it remains stable and continues to perform well. The figure you see on the API donut indicates the viscosity of the motor oil in winter and also, its fluidity after warming up sufficiently. The different additives have various properties, each contributing to the efficient working and life of your car engine. The SAE system for grading motor oils according to viscosity; the suffixes (0, 5, 10, 15 and 25) followed by the letter W designate the engine oil’s “winter” grade. Look to your owner’s manual. It specifies the viscosity grade required for your car’s engine. Today, the most common grades are 5W-30.
Types of motor oils
Additives in motor oils
Motor oil typically contains a Performance Additive Package that can make up 15% to 25% of its composition. The remaining percentage is base oil. The additives help to enhance the performance and viscosity of the motor oil. Oil manufacturers design their products to comply with the specifications of car companies and engine manufacturers. The base oils can vary themselves and assist in managing particulates and oxidation.
API Engine Oil Service Category Charts – Gasoline Engines
Oil API Grade | Zinc (ppm) | Phosphorous (ppm) | Status | Service Gasoline Engines |
SN | 400-750 | 400-700 | Introduced in October 2010 | Introduced in October 2010 for 2011 and older vehicles, designed to provide improved high temperature deposit protection for pistons, more stringent sludge control, and seal compatibility. API SN with Resource Conserving matches ILSAC GF-5 by combining API SN performance with improved fuel economy, turbocharger protection, emission control system compatibility, and protection of engines operating on ethanol-containing fuels up to E85. |
SM | 400-870 | 400-800 | Introduced on 30 November 2004 | Category SM oils are designed to provide improved oxidation resistance, improved deposit protection, better wear protection, and better low-temperature performance over the life of the oil. Some SM oils may also meet the latest ILSAC specification and/or qualify as Energy Conserving. They may be used where API Service Category SJ and SL earlier categories are recommended. |
SL | 1000-1400 | 1000-1400 | 2001 Gasoline Engine Service | Category SL was adopted to describe engine oils for use in 2001. It is for use in service typical of gasoline engines in present and earlier passenger cars, sports utility vehicles, vans and light trucks operating under vehicle manufacturers recommended maintenance procedures. Oils meeting API SL requirements have been tested according to the American Chemistry Council (ACC) Product Approval Code of Practice and may utilize the API Base Oil Interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SJ and earlier categories are recommended. |
SJ | 1000-1400 | 1000-1400 | 1997 Gasoline Engine Service | Category SJ was adopted in 1996 to describe engine oil first mandated in 1997. It is for use in service typical of gasoline engines in present and earlier passenger cars, vans, and light trucks operating under manufacturers recommended maintenance procedures. Oils meeting API SH requirements have been tested according to the American Chemistry Council (ACC) Product Approval Code of Practice and may utilize the API Base Oil Interchange and Viscosity Grade Engine Testing Guidelines. They may be used where API Service Category SH and earlier categories are recommended. |
SH | 1000-1400 | 1200-1400 | Obsolete | For model year 1996 and older engines |
SG | 1000-1400 | 1200-1400 | Obsolete | For model year 1993 and older engines |
SF | 1000-1400 | 1200-1400 | Obsolete | For model year 1988 and older engines |
SE | 1000-1200 | 1200-1400 | Obsolete | For model year 1979 and older engines |
SD | 1000-1200 | 1200-1400 | Obsolete | For model year 1971 and older engines |
SC | 1000-1200 | 1200-1400 | Obsolete | For model year 1967 and older engines |
SB | 1000-1100 | 1200-1400 | Obsolete | For model year 1963 and older engines |
SA | 0 | 0 | Obsolete | For model year 1930 and older engines |
Valve Rocker Lifter Cam Diagram
1 – Valve 2 – Rocker Arm 3 – Valve adjustment screw 4 – Valve adjustment locking nut 5 – Push rod 6 – Hydraulic and non-hydraulic lifter 7 – Flat tappet camshaft and cam lobe |