When the legislation establishing CAFE standards was first passed in 1975, the average fuel economy of vehicles available was about 14 mpg. SAE 10W-40 engine oil was the dominant viscosity grade. Engine oil fuel economy was not even an advertised feature.

A lot has changed since then. The automotive OEMs knew that they needed to improve fuel economy in any way possible. Since viscous drag is a source of energy loss in the engine, they rightly reasoned that reducing the viscosity of the oil would be a step in the right direction. However, the improvement in fuel economy that was gained by going from SAE 10W-40 to SAE 10W-30 was hardly noticeable. The OEMs felt that more drastic reductions were needed.

Obviously there are a number of factors impacting fuel economy, such as engine design, vehicle accessories, aerodynamic drag, tire resistance, inertial mass and driving patterns. Without getting into the details of all of these factors, it should be apparent that engine oil has a relatively limited impact on the overall fuel economy of any vehicle.

So, you ask, why all the fuss about maximizing engine oil fuel economy? Naturally, its all about money. I mentioned the issue of fines. The fines are based on the difference between an automakers CAFE as measured by a prescribed methodology and the 27.5 mpg limit. For every 0.1 mpg an OEM slips below this target, a fine of $5.50 is levied on each and every vehicle sold! If your CAFE is 27.4 mpg, you pay a hefty fine. If engine oil can deliver even a 0.1 mpg improvement, you are home free.

Every Bit Helps

By the mid 80s, the OEMs were feeling a great deal of pressure to meet the CAFE limit of 27.5 mpg. They were forced to change their vehicle mix for mpg even though customers were still clamoring for the more powerful and less-fuel-efficient vehicles. Every bit of fuel economy was crucial.

Meanwhile, there were significant design changes going on in the automobile marketplace. Lighter, more streamlined designs became popular. Smaller, more powerful engines were introduced. More efficient fuel delivery systems, such as fuel injection, were developed.

One of the most important innovations was the introduction of the on-board computer. Originally developed to improve emissions – the other problem affecting OEMs – it became apparent almost at once that the computer could also be used to manage fuel economy. The key to the fuel economy option was fuel injection. By managing the flow of fuel, not only timing-wise but also volumetrically, efficient fuel consumption could be achieved while maintaining the performance which consumers have come to expect.

In 1975, the carburetor reigned supreme. By the early 1990s, fuel injection managed by an on-board computer had completely supplanted the carburetor. (The on-board computer controlling the combustion process was reputed to have more computing capability that the on-board computers which allowed the Apollo missions to go to the moon and back!) In retrospect, the introduction and application of computer technology to the automobile is one of the most amazing feats of the industry.

Oils Burden

The ILSAC labeling system was created as a means of simplifying the engine oil purchase choice for automobile owners. At the time of its introduction, automakers were of the opinion that the American Petroleum Institutes trademarked donut symbol was not clear enough in defining what engine oil requirements were needed for their latest vehicle offerings in the marketplace. APIs was a split system, with fuel economy and engine performance separated (i.e., an oil could have the proper performance credentials but not supply the fuel economy the OEMs desired).

What was then the Motor Vehicle Manufacturers Association began to push for a different,user friendly system to aid automobile owners in making their engine oil purchases. They were especially anxious to get fuel economy into the primary category,insteadofas asupplementtothe API system. They also wanted an evergreen system which would always reflect the latest engine oil needs for their vehicles. To steer this effort, the automakers created ILSAC, the International LubricantsStandardization and Approvals Committee.

ILSACGF-1engineoilforgasoline-fueled vehicles, which first appeared in 1993, set the pattern for subsequent categories. It was essentially API SH engine oil with fuel economy performance added. There was never anything which could really distinguish ILSACGF-1fromSHwith Fuel Efficient performance. Over the next several years, ILSAC GF-2, GF-3 and GF-4 were introduced. Each was matched with an equivalent APIS-series performance level plus fuel economy. Along the way, the OEMs pushed for additional physical and chemical requirements, too, such as gelation index, phosphorus limits and the TEOST bench test for deposit control. AlI of these requirements have been incorporated into the corresponding API designation. What we have, in fact, are two designations for the same oil.

Now the latest upgrade, GF-5, is on the horizon. It continues the progression of more stringent test procedures and limits. Originally targeted for model year 2009, GF-5 is now projected to be in place for 2010 vehicles. Early proposals were for lowered phosphorus limits (to 0.05 percent by weight), a new Sequence IIIH test procedure to wear control, and more emphasis on SAE 0W-XX viscosity grades.

Costly Upgrades

A thoughtful analysis of the requirements for each of the GF categories shows that the test parameters are essentially the same with incremental improvements in performance. Some tests are virtually unchanged, while others have been almost completely redone at significant cost to the oil, additive and automotive industries.

The following is a review of the major tests and what has happened to each.

Rust protection.While not a major test, the Sequence IID was the rust protection standard for many years. However, it was an engine test designed for leaded fuels. Six years ago the IID was dropped in favor of the ball rust test, a much lower-cost bench test which reflected modern fuels. A step in the right direction, according to everyone involved.

High-temperature Oxidation and Deposits. The Sequence III test procedure has undergone three different iterations in the first four GF categories. Every time this happens, the industry inevitably spends several million dollars to develop the procedure and precision. The next version, Sequence IIIH, has been proposed for GF-5 but appears to have been set aside for now. Since the Sequence III (latest version) has been used for base oil interchange purposes, its future seems assured as a part of the GF system.

Low-temperature Deposits. The Sequence V engine test also has changed during the course of the GF lifetime. Industry has debated whether or not all of the measured parameters of the test are necessary. However, the test itself will remain in GF-5.

Fuel Economy. The Sequence VI engine test has seen change three times. Each time, the issues revolved around measuring the durability of the fuel economy effect. Frankly, the durability issue is not for the consumer but for the OEMs. Their CAFE testing protocol has a durability segment which requires a retained level of fuel economy performance after several thousand miles of running.

Chemicals Limits. The physical and chemical tests have reflected changes in phosphorus levels (0.12 percent maximum for GF-1, to between a minimum of 0.06 percent and maximum 0.08 percent for GF-4), the imposition of a sulfur limit in GF-4, and reduced volatility to meet emissions needs. At GF-4 levels, it appears that the OEMs are able to manage their emissions requirements. (Thats not to say legislation may not make it more difficult, or that there are no further improvements that can be made.) It does appear that engine oils may be getting close to their limit on phosphorus levels required to provide adequate wear protection.

Meanwhile, the computer has made the operation of the modern automobile engine about as efficient as possible. Carburetion is gone, as well as the traditional distributor. Combustion is managed to maximize energy and minimize emissions. It allows for more efficient fuel use. The result is fuel economy and emissions controls which meet all current requirements. In fact, these systems are so good they have put the auto industry in the position of making it easy for legislators and other activist groups to demand more!

We have now reached the point where just about every bit of obtainable fuel economy has been captured from engine oil. We are now entering the squeezing blood from a stone phase of fuel economy. It seems to me that it is time to reconsider further changes to engine oils. Perhaps it is time to stop!