Evaluation and Qualification of Gasoline and Diesel Engine Lubricants

Meeting the Future

For more than 65 years, lubricant, additive, and equipment manufacturers have been striving to improve automotive engine oil performance. Southwest Research Institute (SwRI) serves as a technical partner to help clients develop engine oils that meet modern engine requirements and future lubricant performance challenges.

Lubricants for spark-ignited engines are updated as the performance needs of new engines change and as new regulations, such as the 100,000-mile emissions durability requirement for passenger cars, are imposed. Lubricants must not only protect the engine, they must also be compatible with the exhaust oxygen sensor and catalyst. To help vehicle manufacturers meet corporate-average fuel economy standards, industry is developing advanced engine oils that improve fuel efficiency by reducing engine friction.

Diesel engine designs are evolving to meet future emissions and fuel economy requirements. New engines exhibit lower exhaust emissions and greater efficiencies as a result of improved combustion systems, design, and materials, although they challenge fuels, lubricants, and traditional engine oil test procedures.

Diesel Engine Lubricants

To ensure long engine service, lubricants are compared to a series of specifications, such as MIL-L-2104F and API service classifications CD and CF-4. SwRI analyzes lubricants through engine test procedures to determine factory fill, factory branding as genuine oils, and service fill. The Institute performs all recognized test procedures, including:

Mack T6 Mack T8 Mack T9 Cummins L10 GM RFWT Detroit Diesel 6V-92TA

Detroit Diesel Series 60 Caterpillar IM-PC Caterpillar 1K Caterpillar 1N Caterpillar 1P

SwRI has 26 test stands available for the 1G2/1H2/IM-PC1K IN/IP Caterpillar test procedures, which utilize engines representative of heavy-duty diesel engines operating in modern commercial fleets and off-highway applications.

SwRI simulates heavy-duty diesel engine commercial fleet operations in up to 26 single-cylinder test stands.

As diesel engines are modified to achieve low exhaust emissions, new and improved fuels and lubricants evaluation methods are necessary. Changes such as higher fuel injection pressures, electronic engine controls, and higher top ring placement on the piston will help achieve lower emissions. Requirements for low oil consumption and for lubricants that are compatible with oxidation catalysts and capable of maintaining long engine life will result in new or revised additive-treated lubricants.

Changes in diesel fuel mandated by the U.S. Environmental Protection Agency and the California Air Resources Board may require changes in lubricants and additives to improve combustion and to control injector deposits. Opportunities abound for advanced product technology. SwRI offers extensive capabilities in diesel engine lubricants research, including:

• Crankcase oil soot loading
• Diesel fuel additives
• Combustion improvers
• Injector deposit control
• Component wear and life
• New procedures and development of lubricants for alcohol- and natural gas-fueled heavy-duty engines
• Lubricant-emissions relationship studies
• New and revised multi-cylinder and single-cylinder procedures
  • Detroit Diesel
  • Mack
  • Cummins
  • John Deere
  • General Motors
  • Caterpillar 
• Lubricants for advanced technology engines
• Low-friction engine lubricants

In addition to standardized testing, the Institute offers screening tests and other specialized or focused laboratory test procedures.

Gasoline Engine Lubricants

The 288-hour VE engine oil performance test simulates stop-and-go urban and moderate freeway driving.

The Institute offers complete testing services for a variety of four-stroke cycle lubricant specifications, including MIL-L-2104F, SAE, ASTM, and API service classification SJ engine oils.

Standardized testing includes:

• The Sequence IID test, approved in 1978, relates to short-trip service under typical winter conditions in the upper midwestern United States. The test measures how well lubricants inhibit rust and corrosion in the valve train and on the oil pump pressure relief valve. A 1977, 350-cubic-inch (5.7-liter) Oldsmobile V-8 engine, built to precise specifications, operates on leaded gasoline at 1,500 rpm for 30 hours, followed by a 30-minute shutdown and two hours of high-speed (3,600 rpm) operation at elevated temperatures.
  
  
• The Sequence IIIE test, approved in 1987, evaluateshigh-temperature oxidation, sludge, varnish, and valve train wear protection of engine oil. The test relates particularly to high-speed turnpike operation of cars under high ambient temperatures typical of the southern United States. The test is run on a 1986, 3.8-liter Buick V-6 engine specially prepared for this procedure. Fueled by leaded gasoline, the engine operates at high speed (3,000 rpm) and high oil temperature of 300¡F (149¡C) for 64 hours. Oil leveling and sampling are conducted every eight hours.
  
  
• The Sequence VE test is designed to evaluate oil performance in combating varnish and sludge deposits, oil ring clogging, oil screen plugging, and cam lobe and follower wear. The test is run on a 2.3-liter, overhead cam, four-cylinder, Ford electronic fuel injected engine using unleaded gasoline. The engine is operated at low- and mid-range speeds and temperatures for 288 hours, simulating stop-and-go urban and moderate freeway driving.
  
  
• The Labeco L-38 test evaluates how well engine oils minimize bearing corrosion and determines viscosity changes at high temperatures. The test is run on a single-cylinder, 42.5-cubic-inch (0.7-liter), CLR (Cooperative Lubricant Research) engine using leaded gasoline. The test is run at constant speed, temperature, and air/fuel ratio for 40 hours.
  
  
• The Sequence VI-A test, approved in 1996, measures the effects of engine oil on the fuel economy of modern gasoline engine passenger cars and light-duty trucks. The test is conducted on a Ford 4.6-liter V-8 engine, typical of current technology, low-friction valvetrain and piston ring design. Fuel consumption is measured at several steady-state test conditions that relate to recognized Environmental Protection Agency (EPA) driving cycles. The candidate oil is aged for 16 hours, and its performance is compared to a baseline SAE 5W-30 reference oil.

SwRI evaluates bearing weight loss using L-38 standard lubricant test stands.

Gasoline Two-Stroke Cycle Lubricants

Concern over energy conservation and environmental pollution has led to leaner oil-to-fuel ratios, which, in turn, have affected lubricant requirements. Exhaust emission reduction could contribute to the two-stroke cycle engine's viability in the near future. The two-stroke cycle engine provides better power-to-weight ratio, higher specific power output, and less frictional loss than the four-stroke engine. Many major automobile manufacturers have already built experimental fuel-injected, two-stroke cycle engines for automotive applications.

The Institute evaluates lubricants used in two-stroke cycle, air-cooled engines using the ASTM-TC test sequence, which evaluates the lubricant's ability to:

• Resist combustion chamber deposit-induced preignition
• Prevent ring sticking
• Inhibit deposit formation
• Reduce scuffing
• Resist spark plug fouling

SwRI also offers all engine and chemical tests required to evaluate lubricants for two-stroke, water-cooled engines, including the National Marine Manufacturers Association TC-W3TM specification tests. These requirements have led to improved lubricants that exhibit higher levels of resistance to ring sticking and loss of cylinder compression. In the future, biodegradability of lubricants may become a significant factor for lubricants formulated for the boating industry.

For two-stroke, air-cooled engines, the International Standards Organization (ISO) has recently adopted worldwide test procedures to evaluate lubricants for exhaust smoke, exhaust system deposits, lubricity, and piston cleanliness. These test methods, conducted by SwRI, have supplemented the ASTM-TC specification tests previously used by industry.

With trained personnel and modern laboratory facilities, SwRI helps the petroleum industry monitor future trends and develop lubricants that meet current requirements. In addition, SwRI engineering and technical staff members are available to develop and operate special two-stroke cycle laboratory tests or to design and coordinate custom field tests to meet unique requirements.

Advanced Technology

Advanced spark-ignited, two- and four-stroke cycle engines operating on gasoline, alcohol, natural gas, or mixed fuels sometimes require improved or specialized lubricants. Test services are usually customized and frequently incorporate modification of existing test methods.

Following testing, specially trained gasoline and diesel engine lubricants personnel visually rate parts for sludge, rust, varnish, carbon, and wear. SwRI staff members lead industry workshops and help develop new rating aids and techniques.

Institute staff members have expertise in many areas, including:

• European CEC test methods
• Modified Sequence VI: evaluation of fuel/additive effects on fuel economy
• Fuel-efficient engine oil performance in reduced-friction engines
• Alcohol fuels/alternative fuels
  • Engine durability
  • Ring and bore wear
  • Lubricant evaluation
  • Fuel additives 
• Engine/component durability testing
• SAE J1312 engine power mapping
• SAE J1349 engine power test
• Modified sequence tests
• Piston aircraft lubricant tests
• Exhaust valve seat recession
• Induction system deposits
• Port fuel injector deposits/injector flow loss
• Oil-foaming tendency and aeration
• Low-temperature evaluation
• Turbocharger durability and lubrication
• Real-time kinematic viscosity

The Institute's experienced staff members provide special assistance in experimental projects to develop customized test procedures and precise test equipment for measurement and control.

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