One simple change may be for drivers at last to swear off SAE 10W-30 and 10W-40 engine oils. But theyll need some persuading, as Fords Charlie Sherwood told LubesnGreases over five years ago: Our fathers and grandfathers used these oils, and the prevailing attitude among many consumers is that thicker is better.

This writer recently contacted some major automakers for their current views on the subject.

Ford has been recommending SAE 5W-20 oil since its 2001 model year, including oil-fill-cap labels identifying the lighter viscosity grade. Fords Mike Riley indicates that lower viscosity oils continue to be of interest to save fuel for customers and help protect our environment. For example, using SAE 5W-20 oil increases fuel economy by about 0.5 percent compared to 5W-30 oil, he observed. This equates to a fuel savings of 125 million gallons per year when its used in all applicable Ford vehicles.

Since its introduction in Fords 2001 models, 5W-20 oil has saved up to 640 million gallons of gasoline in the United States, Riley added, or an equivalent 5.6 millionmetric tons of carbon dioxide emissions. This savingsiseven more when SAE 5W-20 oil replaces the use of aheavier oil like 10W-30.

At the same time, Honda R&D Americas Principal Chemist Jeff Jetter noted that his company has used low-viscosity oil in Japan for a number of years, and that 70 percent of its 2001 model year new cars came with SAE 5W-20 in the crankcase; within a few years, that rose to 90 percent. He said his company believes the fuel economy improvement provided by 5W-20 is important.

In September,Jetter again focused on fuel economy. Lower viscosity oils provide better fuel economy,thats beyond question, he said. Currently our Civic hybrid model is factory filled with SAE 0W-20 and thats our service-fill recommendation, too. And we will transition to 0W-20 for most of our cars in the next few years. However,the big challenge right now for us is availability of 0W-20 oils in the retail market.

Jetter added, Weve been headed in the general direction of lower viscosity oils for anumber of years for fuel economy reasons. With modern engine technology you just dont need the heavier oils any more. And durability is not a problem at all, none whatsoever; if there were even a modicum of concern we wouldnt go there.

Dennis Florkowski, supervisor and senior specialist in Daimler Chryslers Fuels &Lubricants Group, also is thinking light: Our highest-volume viscosity grade usage as we move into the next model year is the SAE 5W-20. However,westill have limited need for the other ILSAC Grades of SAE 5W-30 and 10W-30. This would apply to all North American gasoline applications except our SRT High Performance Line; the SRTs are filled with an SAE 0W-40.

I am sure that with certain base oils, newer additive technologies and controlled viscosity profiles, that an SAE 0W-20 could be utilized to enhance fuel efficiency in both [Corporate Average Fuel Economy requirements] and the real world while retaining the oil robustness needed to support our maintenance intervals, Florkowski continued. I also suspect this would be a high-cost product. DaimlerChrysler believes that viscosity grade selection to enhance fuel efficiency is the best alternative,as opposed to significant additions of friction modifying additives. We are expanding the use of SAE 5W-20 throughout our fleets; however, we currently are not considering the 0W-20 grade.

At General Motors Powertrain, Bob Olree pointed to his companys unique perception.Our primary engine oil recommendation for all of our gasoline engines is SAE 5W-30. This includes the ultra-high-performance 505-hourse power Z06 Corvette and supercharged Cadillac engines. There are definite advantages for GM owners and service technicians in having a single SAE viscosity recommendation.

Olree added, At extremely low temperatures GM does recommend that owners consider using SAE 0W-30 or synthetic SAE 5W-30 oils, and we are continually evaluating our viscosity recommendation.

Toyotas Hannah Murray, a lubrication and regulatory engineer,pointed out, Fuel economy is very important to our customers; its a big deal, and lower viscosity oils provide a clear fuel economy benefit.

She added, Currently some of our most popular models, including the 4-cylinder Camry and Rav4, are factory filled with 0W-20 oil, and we recommend that owners use this grade when changing their oil. While SAE 5W-30 is the current recommended oil for the rest of our fleet, our new engine technology is compatible with 0W-20 oil, and we will continue to look for opportunities to introduce the product into our model line-up.

5Ws: Mainstream Now

While not universally accepted by vehicle manufacturers for their factory or service fill, 5W-20 oils have become a mainstream option. Their fuel economy benefits are clear,and high gasoline prices may push other OEMs and consumers in their direction.

In 2001, when Ford initiated its SAE 5W-20 factory fill, it was difficult to find the unfamiliar grade at many large aftermarket retailers. That has changed. For example, in late August, Northern Virginia outlets of PepBoys, AutoZone and Wal-Mart all displayed SAE 5W-20 products from most national brands as well as their house brands.

Its another story for SAE 0W-multigrades; not one 0W-xxoil was for sale in those same outlets.

Sustained higher gasoline prices may prompt more consumers to consider the fuel economy benefits in some motor oils. But are retail shelves devoid of SAE 0W-xxoil a testament to consumer indifference? to habit (our fathers thicker is bettermotto, as Charlie Sherwood reminded us)? Or to misleading public information by experts?

Unclear on the Concept

Take,for instance, the following exchange in the Trenton, N.J.,Times. In April 2005, Junior Damato, who writes the papers Ask the Auto Doctorcolumn, received a readers query: Our 1999 Plymouth Voyager, with 66,756 miles, we use for mostly supermarket and doctors visits. Our son in Denver says to switch to SAE 0W-30 synthetic oil and synthetic transmission fluid. I had these products shipped here from Denver. Our dealer refused to install them and so did the local repair shop, which has annoyed us and our son. Our son says the synthetic fluids will give me us a lot better fuel mileage. What should we do?

The Auto Doctor responded, The new 0W-30 synthetic oil is for cold climate use. It is not intended for use in warm states. 5W-30 synthetic engine oil can be used in 99 percent of all climates. The 0W-30 should only be used in very cold climates, during the very cold months. As for the transmission fluid, use only Chrysler transmission fluids or an equivalent that meets Chrysler specs. Iwould send the fluids you bought back to your son.

Andy Jackson, senior scientific advisor at ExxonMobil and chairman of the SAE Engine Oil Viscosity Classification Task Force, has a different take on this. While he agrees with Damatos comment about using only transmission fluids that meet a car manufacturers specifications, he said, The perception that SAE 0W-30 engine oil should only be used in cold climates is just not correct. SAE Standard J300 requires SAE 0W-30 oil to provide the same viscosity at high temperature as SAE 5W-30, for protection in all climates, yet the SAE 0W-30 oil will improve fuel economy over the SAE 5W-30 due to its lower viscosity,not only during start up, but also during the warm-up phase in both warm and cold climates. We cant ignore the fuel economy benefits of SAE 0W-xx viscosity grades of engine oil.

Jackson added, If one is to advise against using them, it should be for the appropriate reasons. To avoid misunderstanding about this type of product in the future, additional education about SAE 0W-xx grade oils is needed.

Higher Reason

Field testing is the gold standard for evaluating engine oils. When field tests are very carefully designed,managed and controlled,there can be a high degree of confidence in outcomes.

That is the case with a rigorous test conducted from the spring of 2003 through the end of 2004, involving eight Las Vegas taxicabs. Las Vegas is considered one of the most demanding environments for an engine lubricant in North America, where cabs experience significant idle time and summer temperatures can exceed 108 degrees F.

The test evaluated the relative performance of prototype SAE 0W-20 and 5W-20 GF-4 oils. Both oils contained the same additive technology,formulated with a low 0.05 percent-mass phosphorus. Only API Group II/II+ base oils were used.

The study was a joint effort by Petro-Canada, Infineum and Ford, and used eight 2001 model year Ford Windstar vans, equipped with 3.8-liter V-6 engines. Four of these were filled with SAE 5W-20 oil and four with 0W- 20. A drain interval of 10,000 miles was selected -more than three times the drain interval Ford recommended for this type of severe service. Oil samples were taken at 5,000,7,500 and 10,000miles,and standard used oil analysis was conducted on these samples by an independent laboratory. The test duration for each vehicle was 100,000 miles.

Petro-Canadas Amanda Damen, Infineums Nigel Broom and Rolfe Hartley, and Mike Riley of Ford reported on this work to SAE International in San Antonio last October. Their paper noted, There has been much work in demonstrating the effectiveness of SAE 0W in low-temperature environments, so it was agreed the industry generally accepts the low-temperature performance benefits of such a fluid. The field trial was therefore designed to demonstrate in a high-temperature environment other factors, specifically: That SAE 0W-20 is equivalent to 5W-20 in durability, equal or better in oil consumption and deposit control, demonstrates equal or superior fuel economy,and presents no harm data in wear performance.

A tall order.

Both the SAE 5W-20 and 0W-20 oils showed equivalent performance in all used oil analysis parameters, the research team reported. Both oils showed excellent durability in severe fleet service at lower ZDDP levels, and 0.05 percent phosphorus. [Thats actually below the ILSACGF-4oils required minimum of 0.06 percent.]Bench tests confirmed that both oils provide good oxidation and viscosity control.

The base stock system in combination with the additive technology demonstrated good wear protection even with reduced phosphorus levels -supported by the used oil analysis in combination with engine ratings and additional bench friction tests, the report continued. There was no sign of any premature engine damage nor premature oil thickening. This finding takes on added importance in view of the very long drain intervals and severe operating environment.

Looking at fuel economy, the researchers noted that SAE J300 specifications limit fuel economy for the 5W-20 grade, because formulations must not drop below a minimum level for cold cranking.SAE 0W-20, however, is not restricted [by cold cranking limits] and therefore allows more room for optimization.

The team found, Directional fuel economy improvement was demonstrated for 0W-20 over 5W-20 oil, with an overall improvement in average fuel economy of 0.2 MPG for the vehicles using 0W-20 over those using 5W-20. This observation was especially interesting as the data came from all units and were operated by a variety of drivers.

And, there were no low-temperature control issues and 0W-20 performs equivalently to 5W-20.

However,the team added dryly,There is also some consumer concern about 0W or thin motor oils.