As automotive technology continues to evolve, so do the motor oils that lubricate today’s engines. Though our government has not raised Corporate Average Fuel Economy (CAFE) requirements in a long, long time, they would like to see significant gains in fuel economy to reduce our dependence on foreign oil. Former Vice President Al Gore would also like us to burn less gas so we can reduce carbon dioxide (CO2) emissions that are contributing to suspected global warming. Making motor oil more slippery is one way to accomplish both of these goals.
By reducing friction with (1) better base stocks, and/or (2) more friction modifiers in the additive package, a low friction motor oil can reduce parasitic horsepower losses inside the engine allowing the engine to deliver better fuel economy.
According to vehicle tests that have been run using the Federal Test Procedure (FTP) — which is the same test procedure auto makers currently use to certify vehicle emissions compliance — some of these new next-generation, low-friction motor oils are delivering 1-2% better fuel economy over today’s commercially available oils.
A couple of percentage points may not sound like much of an improvement, but if applied across the board to the entire U.S vehicle fleet of 230 million cars and trucks, it could save 1.4 to 2.8 billion gallons of fuel a year! Those kind of numbers would have a significant impact on our balance of payments for foreign oil, not to mention CO2 emissions.
Certifying Motor Oil
Most of you are probably familiar with the American Petroleum Institute (API) and the API “Starburst” certification logo and service symbol “donut” that appears on all licensed containers of motor oil that meet API specifications. API has various motor oil classifications that are based on OEM lubrication requirements and various industry testing procedures.
The current API service categories for gasoline engines include:
SM – Introduced Nov. 30, 2004 for 2005 model year engines. 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.
SL – A current classification for 2004 and older engines.
SJ – A current classification for 2001 and older engines.
Any API rating from SH back to SA is considered obsolete and not suitable for newer engines.
Of course, API isn’t the only body that certifies the quality and service classifications of motor oil. Various aspects of motor oil testing have come under the auspices of the Society of Automotive Engineers (SAE) and the American Society of Testing Materials (ASTM). So back in 1992, the International Lubricant Standardization and Approval Committee (ILSAC) was formed to consolidate and coordinate standards for motor oil testing for North American and Japanese auto makers. ILSAC developed minimum performance standards for gasoline-powered passenger car and non-commercial light truck oils, which later became known as GF (Gasoline Fueled) motor oil standards.
Motor oils that meet ILSAC GF standards usually meet similar API standards, but not always. The test and certification procedures are somewhat different. But for the average end user, the important point is that motor oils are required to meet certain criteria. So here’s a little history on what’s occurred so far.
The first GF-1 standard was established in 1996 the same time that API announced its SH service classification. The new classifications limited the amount of phosphorous in motor oil to 0.12%, a level the Environmental Protection Agency wanted to extend the life of catalytic converters (phosphorus contaminates the catalyst and causes it to age).
In October 1996, ILSAC announced its new GF-2 specification at the same time API released its new SJ service classification. The new standards reduced phosphorous even more to a limit of no more than 0.10%. The new standards also set higher benchmarks for low-temperature operation, high-temperature deposits and foam control.
In 1997, API also announced a new “Energy Conserving” rating for motor oils that demonstrated improved fuel economy. To qualify as an Energy Conserving motor oil, 5W-20 and 0W-30 oils had to show a 1.4% improvement in fuel economy over a standard reference oil, 5W-30 oils had to show a 1.1% improvement, and 10W-30 oils had to show a 0.5% improvement.
The Energy Conserving rating was based on a test procedure known as Sequence VI-A, which replaced an earlier test method and used a Ford 4.6L overhead cam V8 instead of a Buick 3.8L pushrod V6.
In July 2001, the next round of standards were announced. These included the new ILSAC GF-3 and API SL classifications. As with the previous ratings, the bar was raised once again for emissions durability, fuel economy, volatility and deposit control, viscosity retention, additive depletion over the service life of the oil, and oil consumption rates.
The next round of specifications, the ILSAC GF-4 and API SM ratings, didn’t arrive until November 2004 for model year 2005 vehicles. The new ratings included a new fuel economy test (Sequence IV-B), improved fuel economy requirements, enhanced oxidation and piston deposit control (20% better), and better low-temperature pumpability as the oil ages (a new requirement for GF-4). Oils that meet the ILSAC GF-4 and API SM ratings also have lower phosphorous (0.08%) and sulfur levels (0.5-0.7% depending on the viscosity grade) to allow catalytic converters to last up to 120,000 miles or longer.
GF-5 Will Be Next
ILSAC is now working on developing a fifth generation motor oil rating called GF-5. The goal is to have the new standard ready to go by mid-year 2009 for the 2010 model year vehicles. Like all the previous ILSAC and API standards, GF-5 motor oils will have to be backwards compatible to accommodate all the older vehicles that are on the road.
The auto makers as well as the oil companies say a new GF-5 certification procedure is needed to take oil performance to the next level, and to better document the fuel-saving benefits of friction-modified oils. The current GF-4 test laboratory procedures do not produce the same kind of fuel economy numbers that are seen on an FTP emissions certification test, so engineers are developing a new Sequence VI-D engine test procedure that will more accurately evaluate gains in fuel economy. The Japanese auto makers would also like to see a new timing chain wear test added to the GF-5 specification.
The current objectives of the GF-5 program are:
To increase fuel economy compared to current GF-4 oils.
To improve high-temperature, high-load lubrication performance.
To reduce deposit formation.
To reduce the level of chemical impurities in the oil, and their impact on emission control components (which probably means even lower phosphorous and sulfur levels).
To extend oil change intervals (possibly as high as 8,000 miles or longer).
Most of the issues surrounding the coming GF-5 oil standard have to do with engineering test procedures that are obsolete or need to be changed. The current Sequence IV-B fuel economy test, which is done in a laboratory on a test bench, will have to be replaced with some type of engine dynamometer test that more accurately simulated real-world driving conditions. The new test procedure should be ready by early next year.
Another concern is that some of today’s GF-4 oils may not lubricate timing chains adequately, so a chain wear test or roller follower test may be added to the GF-5 standard. There has also been discussion about adding an oil aeration test that would measure the effect of air bubbles in the oil on lubrication.
GF-5 may also require reducing phosphorous and sulfur even more to extend the life of the catalytic converter to 150,000 miles and beyond. Phosphorous and sulfur can contaminate the catalyst and reduce the life of the converter if the engine uses oil. But both of these ingredients are also important anti-wear agents, so the fear is that reducing phosphorous and sulfur too much may end up reducing the life of the engine itself.
There are already concerns that today’s levels of phosphorous may be too low for older pushrod engines with flat tappet camshafts. Camshafts with flat-bottom lifters generate a lot more friction between the cam lobes and lifters than roller cams with roller lifters. Consequently, cam lobe wear in older engines may be a problem if the oil does not contain adequate levels of anti-wear agents, or if the oil is not changed regularly.