Motor Oil Tests Reveal Which Brand is the Best Synthetic Motor Oil – See Comparison Charts

Ten competing 5w30 synthetic motor oils were subjected to a series of motor oil comparison tests. All five tests were completed in accordance with American Society of Testing and Materials (ASTM) test procedures, with the results directly indicating the level of protection and performance provided by each of the motor oils tested. Below are descriptions of each of the tests and the motor oil ratings for each of the oils tested. Comparison charts make it easy for you to determine which brand is the best synthetic motor oil.
Because synthetic motor oils continue to demonstrate strong annual growth, whereas conventional motor oil sales remain flat, the motor oils chosen for this comparison were all synthetic. Motorists now recognize that synthetics legitimately improve engine performance and many vehicles today leave the factory with synthetic oil installed and recommended as the service fill, contributing to synthetics’ increased demand. Oil manufacturers have responded. Many now formulate multiple synthetic engine oils, often led by a flagship product that represents each company’s most advanced technology. The objective of this study is to compare the performance and cost-effectiveness of AMSOIL Signature Series Synthetic Engine Oil to several passenger-car/light-truck synthetic motor oils widely considered by marketers and consumers to be the best available.
Motor Oils Tested
The following 10 synthetic motor oils were selected. All oils were 5w30 and are recommended for the American Petroleum Institute (API) SN and International Lubricants Standardization and Approval Committee (ILSAC) GF-5 performance specifications:
AMSOIL Signature Series Synthetic Motor Oil
Castrol Edge with Titanium Fluid Strength Technology
Lucas Synthetic
Mobil 1 Extended Performance
Pennzoil Ultra
Petro-Canada SUPREME Synthetic
Quaker State Ultimate Durability
Red Line High Performance Motor Oil
Royal Purple High Performance Motor Oil
Valvoline SynPower Full Synthetic
ASTM Tests Performed
Laboratory bench testing, conducted in accordance with American Society of Testing and Materials (ASTM) procedures, examined several important areas of motor oil performance, including resistance to deposit formation, wear protection, high-temperature stability, resistance to acid formation and cold-temperature performance. Bench tests are used widely to differentiate between formulations. Testing was completed February 2013 by an independent, third-party lab. The following tests were performed on each of the motor oils:
Four-Ball Wear Test (ASTM D4172 Mod.)
Total Base Number (ASTM D2896)
Cold Cranking Viscosity (ASTM D5293)
Thermo-Oxidation Engine Oil Simulation Test (TEOST) (ASTM D6335)
NOACK Volatility Test (ASTM D5800)
Cost Comparison Reveals AMSOIL Saves Money
Cost comparisons show that drivers save money with AMSOIL.
Four-Ball Wear Test (ASTM D4172 Mod.)
The Four Ball Wear Test evaluates the wear protection that an engine oil provides. Although not widely used as an engine oil test, the Four-Ball Wear Test provides a means of comparing relative wear-protection properties of lubricating oils.
The Four Ball Wear Test puts one rotating ½-inch diameter steel ball against three fixed ½-inch diameter steel balls, which are covered with the test lubricant, under specific conditions of pressure, temperature, revolutions per minute and duration. (To better differentiate between lubricants, the severity of this test was increased with higher rpm and temperature). Wear scars are then measured and averaged; the size of the scar determines the amount of wear protection the lubricant provides.
The smaller the wear scar, the better the protection.
- Extends engine life
- Major repairs are often reduced
- Reduced downtime and maintenance expenses
Total Base Number (ASTM D2896)
Total Base Number (TBN) is the measure of a lubricant’s reserve alkalinity, which aids in the control of acids formed during the combustion process. Most passenger car motor oils offer only 7 TBN and are formulated with detergents that quickly lose TBN value. With TBN loss, oils lose their ability to neutralize acids, prevent high-temperature deposits and inhibit rust. TBN can also be used as a measure of lubricant degradation in service; TBN loss is a primary reason oils require changing.
Motor oils that have a high TBN and demonstrate good TBN retention are known to effectively reduce the corrosive effects of acids over an extended period.
- Suspends wear-causing contaminants
- Longer oil life, reducing oil changes and saving time and money
Cold Cranking Simulator Test (ASTM D5293)
The Cold Cranking Simulator Test determines the apparent viscosity of lubricants at low temperatures and at high shear rates. Viscosity of lubricants under these conditions is directly related to low-temperature engine cranking. The test results are used to assign SAE “W” grades. The test was performed at -22ºF (-30ºC). Results are reported in centipoise (cP). To meet the API SN and ILSAC GF-5 motor oil specifications, a motor oil’s cold crank viscosity must not exceed 6,600 cP.
The lower a lubricant’s cold crank viscosity, the easier an engine will turn over in cold temperatures. (Oils that thicken too much in cold temperatures won’t allow engines to turn fast enough to start.)
- Reduces drag on moving engine parts
- Allows engines to achieve critical cranking speed in frigid temperatures
- Engines turn over quickly and dependably in the coldest winter temperatures
- Oil flows quickly to engine parts for critical start-up protection
- Wear is greatly reduced
- Reduces strain on battery
Thermo-Oxidation Engine Oil Simulation Test (TEOST) (ASTM D6335)
Motor oils can form deposits when exposed to increased heat, reducing efficiency and contributing to poor overall performance. Given the number of vehicles now equipped with direct fuel injection, turbochargers and other performance-enhancing technologies that increase heat, deposit control has taken on increased importance. To meet the API SN Resource Conserving and ILSAC GF-5 motor oil specifications, a 5w30 motor oil must limit total deposit formation to 30 mg or less.
According to the ASTM, the TEOST test method “is designed to predict the high-temperature deposit forming tendencies of an engine oil. This test method can be used to screen oil samples or as a quality assurance tool.”
NOACK Volatility Test (ASTM D5800)
The NOACK Volatility Test determines the evaporation loss of lubricants in high-temperature service. The more motor oils vaporize, the thicker and heavier they become, contributing to poor circulation, reduced fuel economy and increased oil consumption, wear and emissions. The NOACK provides a basis for estimating the approximate useful life of a lubricant.
In the NOACK, a test specimen of oil is heated to 482°F and held at that temperature for one hour. After an hour, the remaining oil volume is weighed and compared to the original weight, with the difference reported as the percentage of weight lost. The NOACK Volatility Test was developed in Germany and has long been a specification test for European motor oils. Volatility testing became a requirement for North American motor oils in 1992, with the introduction of API SH/ILSAC GF-1 oils. Volatility standards were tightened with the 1996 introduction of API SJ/ILSAC GF-2 oils, which required a weight loss limit of 22%. Results must be limited to 15% or less to meet the current API SM/ILSAC GF-4 specifications.
According to the ASTM, “Evaporation may contribute to oil consumption in an engine and can lead to a change in the properties of an oil.” As with the TEOST test, low values in the NOACK Volatility Test are of particular benefit in modern, hot-running engines. Lubricants with low NOACK scores are preferred; the lower the number, the better the resistance to vaporization. Low NOACK scores indicates an oil that will keep their original protective and performance qualities longer.
- Better oil circulation
- Maximum fuel efficiency
- Reduced oil consumption
- Less deposit formation
- Stable viscosity for low and high temperature wear protection
- Fewer emissions
- Longer oil life, reducing oil changes and saving time and money
Cost Comparisons
The value comparison chart below shows how much money a motorist would spend on each of the oils tested and the number of oil changes required.
The above tests prove AMSOIL’s ability to safely extend oil drain intervals, but the value comparison chart below illustrates what an impact AMSOIL will have on your time and wallet. AMSOIL saves drivers both time and money!
Conclusion
AMSOIL Signature Series Synthetic Engine Oil ranked first in four of the six motor oil comparisons. In contrast, while some oils performed well in a few areas, they did not perform as well in others. Different results from one test to another indicate an emphasis in one area of performance does not correspond to increased performance in other areas of testing. It also reveals the difficulty inherent in formulating a high-quality motor oil that performs well in tests designed to assess optimum engine protection and life.
As engines continue to evolve and demand more from motor oil, the need for premium lubrication becomes more critical. Industry-standard testing performed by an independent, third-party laboratory reveals AMSOIL Signature Series Synthetic Engine Oil to be the overall top-performing oil in these tests. When considering the savings of time and money available due to its 15,000-mile/one-year drain interval in severe service, Signature Series is also the most economical motor oil.