Im sure you have heard of the law of diminishing returns. But in case you havent, it goes something like this: After a certain point, the more effort and resources you put into something, the less you get in return. What does this have to do with oil? Stick with me for a while and Ill try to clarify.
Back in the mid 70s, the U.S. Congress approved a bill setting a minimum fuel economy requirement of 27.5 miles per gallon on average for all automobiles and light-duty trucks – basically, all gasoline-fueled vehicles sold in the United States. Automakers had until the 1985 model year to achieve this level of performance, which was to be a weighted average of all vehicle, engine and transmission combinations they produced each year. The scheme known as Corporate Average Fuel Economy, or CAFE, was developed to measure the results.
At the time, most automobiles on U.S. roads were getting around 15 miles per gallon, with the exception of those like the Volkswagen Beetle or the Japanese entries in the marketplace. Obviously, North American original equipment manufacturers were going to have to do some pretty fancy engineering in order to hit that seemingly huge challenge.
Well, as you know, they did it – but just barely. In fact, for the first few years they had to do some clever bookkeeping which allowed them to bank credits on early results that could be applied to later model years. By the end they were able to make the limit with more and more ease.
The OEMs did this with a combination of smaller and lighter vehicles as well as smaller and more efficient engines and transmissions. Of all the innovations that turned the tide, I personally think the on-board computer stands at the head of the class. That allowed the OEMs to remove the carburetor, which is not as efficient at fuel management, and go to computer-managed fuel injection that precisely controls when and how much fuel is used based on driving conditions. In addition, the computer allowed much better control over vehicle exhaust emissions, which were another source of lost fuel economy.
Fast-forward now to 2007, when Congress passed the Energy Independence and Security Act, legislating the use of renewable fuels in order to cut down on crude oil consumption and reduce emissions. Ethanol, mostly made from corn, was the ready answer and within a few years most gasoline sold was dosed at about 10 percent (E10). The law also imagined a constantly growing vehicle population and simultaneous growth in fuel demand, so it set escalating targets for ethanol production in order to keep up with the 10 percent requirement. Ethanol does provide some emissions improvements in carbon dioxide levels but sacrifices energy content in the fuel, essentially reducing fuel economy by an estimated 1 to 2 miles per gallon.
Right on time, 2008 saw the downfall of the economy and a reduction in fuel use. The ethanol regulations didnt change so several ethanol producers were stuck with lots of excess alcohol that had no home. They pushed for a relaxation to 15 percent ethanol for the coming years, and EPA agreed to allow E15 to be offered. But this move met with resistance from the automotive OEMs and the small-equipment engine manufacturers who feel thats too much ethanol. On top of that, fracking became all the rage and U.S. crude production ramped up, generating at latest count an additional 1.5 million to 2 million barrels of crude daily. With ample crude and less dependence on foreign sources, oil prices fell.
In 2011 Congress passed regulations which are now leading to the next great step forward in fuel economy. Effective with the 2017 model year, CAFE will jump to a minimum of 35.5 mpg, while emissions requirements also stiffen.
Unfortunately for consumers, the miles per gallon metric is misleading, because a vehicles mpg doesnt follow a linear relationship with the fuel it uses over, say 1,000 miles. EPA coined the term the mileage illusion to describe this discrepancy. Rather than mpg, the agency would like to see the fuel economy metric become gallons per 1,000 miles, similar to how Europeans measure fuel economy and report it in liters per 1,000 kilometers. However, mpg is whats required by law to be displayed on the new-car window stickers you see in dealer showrooms.
The graphic on page 6, from the EPA, illustrates the gap very clearly. It shows the fuel savings for a vehicle that gets 10 mpg versus one that gets 15 mpg is about 33 gallons over the course of 1,000 miles. On the other hand, that same 5 mpg jump in fuel economy for a 35 mpg versus a 30 mpg vehicle only yields actual fuel savings of about 5 gallons over a 1,000-mile span.
OK, so we now have a metric that shows how fuel economy should be calculated; gallons per 1,000 miles, or gal/1K miles. What metric should we use to show how much fuel is saved by using an ILSAC GF-5 or API SN Resource Conserving engine oil?
Under the API engine oil system, fuel economy is determined by the Sequence VID engine test, which measures the fuel economy improvement after 16 hours of testing and again after 100 hours. The two numbers are then added together to get the total fuel economy improvement, or FEI SUM. Each oil viscosity grade must show some minimum improvement to claim resource conserving as shown in the table below.
Referring again to EPAs Mileage Illusion graph, 27.5 mpg results in fuel consumption somewhere north of 36.3 gal/1K miles. Suppose now we use an SAE 0W-20 engine oil. Such an oil must supply a 2.6 percent improvement in overall fuel economy; that would lift us to 28.2 mpg.
Converting that number into gal/1K miles results in a value of about 35.5 gallons. That is, for that 2.6 percent improvement in fuel economy, we save less than 1 gallon of gasoline per 1,000 miles.
The next engine oil category upgrade, API SP and ILSAC GF-6, is supposed to provide even more fuel economy improvement as shown below.
For 2017, the CAFE requirement rises to 35.5 mpg, equal to about 28.2 gal/1K miles, according to EPAs graph. With ILSAC GF-6 contributing another 3.6 percent, for the SAE 0W-20 grade, well reach 36.8 mpg or 27.2 gal/1K miles – a savings of 1 gallon per thousand miles driven. Again, the gain is small for required fuel savings.
Part of this gain is due to the reference oil viscosity (SAE 20W-30). However, theres no doubt that friction modification does help. The real hero will be the viscosity of the oil itself. That property is being pursued vigorously with the introduction of SAE 8, SAE 12 and SAE 16 grades to the latest edition of the engine oil viscosity grade classification system (SAE J300-JAN2015).
Ive noted before the twin concerns I have regarding reduced viscosity for engine oils; namely engine durability, and availability of sufficient low-viscosity base oils with suitable volatility.
Do we really need to continue chasing viscosity and friction modification when the gain is so small, and these very substantive difficulties – durability, base oil availability, volatility – loom so large? I know that in the early going, 20-plus years ago, engine oils contribution was vital for the OEMs to make sure they met their CAFE requirements. The small gain from the best FE oils available in the marketplace could spell the difference between success and a federal fine of $10 per vehicle per 0.1 mpg below the limit – across an entire years sales. Thats big bucks for Ford, General Motors and Fiat/Chrysler.
There is an additional concern here and it comes hard on the heels of the 35.5 mpg mandate for the 2017 model year. The auto industry next faces a CAFE requirement of 55 mpg by 2025. The industry had 10 years to get from 15 mpg to 27.5 mpg. Theyve had what amounts to a 30-year lead time to work up to 35.5 mpg (although it has only been six years since that limit was imposed and implemented). In essence, the time crunch for making the leap to 55 mpg is shorter and the limits are more drastic.
All in all, engine oils are being worked very hard for very little gain and at great risk. And it looks to me like the law of diminishing returns is really starting to take its toll. z
Industry consultant Steve Swedberg has over 40 years experience in lubricants, most notably with Pennzoil and Chevron Oronite. He is a longtime member of the American Chemical Society and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg
@cox.net.