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Way back in my formative years, I drove a truck to put myself through college. Actually, there were two trucks, one a 1947 International and the other a brand new 1960 GMC. Both were gasoline-fueled dump trucks and both were a bear to handle. The 47 International didnt have synchromesh gears so it required double-clutching. The GMC had a very wide V-block engine, making steering very tough. I didnt maintain them, but my best guess is that they were being lubricated with the local service stations MS rated forecourt engine oil. (As a precaution, I kept my commercial drivers license for years, just in case my new profession in the oil business didnt work out.)

Lets fast-forward to today and review the current status of heavy-duty engine oils. Among the highlights:

The current engine oil category, API CJ-4, was introduced in 2006 and is very successful.

The viscosity grade of choice on U.S. roads is SAE 15W-40.

The U.S. uses ultra-low sulfur diesel, 15 ppm maximum.

Engines now have sophisticated emissions control systems.

Truck designs now incorporate advanced aerodynamics for better fuel economy.

Transmissions and axles operate on long-life lubricants which offer fuel economy benefits.

Bottom line is that heavy-duty engine oil is working well, emissions are under control, and fuel economy benefits are being captured. What more could there be to affect this market?

Lets start with the ASTM Committee D-2 meeting just concluded in June in Kansas City. At the Heavy Duty Engine Oil Classification Panel meeting, Greg Shank of Volvo/Mack Powertrain, who chairs the Engine Manufacturers Associations lubricants committee, gave a one-slide summary of how engine builders view engine oil. Among the items he raised were the possibility of a performance change in 2015 and the specter of a fuel economy mandate for heavy-duty engines by 2016-17. He also listed some additional issues and requirements that might be felt, including an oxidation test, TAN depletion, shear stability, aeration test, turbocharger deposits, and fuel economy testing.

At the same meeting, Mark Cooper of Chevron Oronite reported on the status of current heavy-duty engine tests. Cooper had polled ASTMs surveillance panels as to the number of parts that are available and how long the supply is expected to last. Currently, there are sufficient parts to last only until 2015. At that time, a new heavy-duty engine oil category could be required because some of todays engine tests will be obsolete.

In addition, Cooper noted, the HEUI air entrainment test is questionable due to test discrimination issues, and the roller follower wear test (RFWT) is among those running out of parts. Many consider the RFWT to be redundant with the Cummins ISB and ISM wear tests, and removing a seemingly redundant test from a category would seem to be a no-brainer. But protocols must be followed and a demonstration made that removing the test will not impact the integrity of the CJ-4 category, before the RFWT can be dropped.

Fuel economy is another subject for consideration. Shank touched on it, but it is a lot more than just a fleeting thought. A new congressionally mandated report from the National Research Council published March 31, 2010 ( php?record_id=12845) analyzed the various factors involved in improving fuel economy of medium-and heavy-duty trucks. New federal regulations addressing truck fuel economy take effect next July, with the first limits on fuel economy to be established in 2014 and then grow tougher over time. There is general agreement that improvements in such things as aerodynamics, tire technology and auxiliary power units, as well as revisions in drive train lubricant viscometrics, will enable the trucking industry to meet fuel economy mandates until 2017. At that time though, we will reach what is being described as technology forcing limits. These will require changes beyond current capabilities, meaning a new heavy-duty engine oil category is probable.

In North America, we measure passenger car fuel economy as miles per gallon. The logic is clear: How far can you go on one gallon of fuel? Europe reverses the question, and measures fuel economy as liters per 100 kilometers. The logic here: How much fuel will you need to go a specific distance? Both of these approaches are based on moving a light-duty vehicle.

For trucks in commercial operation, the question is more complex. Is it appropriate to measure simply the miles per gallon, or is there a better metric such as a load-specific fuel consumption (i.e., gallons per ton-mile). Think of it this way: For a modern, well-designed and well-maintained Class 8 tractor-trailer combination, standard fuel economy is about 8 mpg. However, this combination is hauling 80,000 pounds (40 tons) so its load-specific fuel economy is 0.003 gal/ton-mile. Its hard to get your mind around that, isnt it?

In an SAE paper last year entitled The Lubricant Contribution to Improved Fuel Economy in Heavy Duty Diesel Engines,(SAE 2009-01-2856), Chevron Oronite researchers Wim van Dam, Peter Kleijwegt, Marnix Torreman and Gary Parsons discussed a standardized laboratory engine test for measuring heavy-duty fuel economy. This dynamometer-based test was developed by Volvo and uses a D12D Volvo engine under 13 varying torque and speed regimes.

Some of the results obtained by van Dam and his colleagues in their Rotterdam laboratory were quite interesting. For instance, they measured the effects of viscosity grade, comparing SAE 15W-40, 10W-40, 5W-40 and 15W-30 grades. Table 1 outlines the results as measured in both on-highway and so-called hilly conditions.

Clearly fuel economy, in this test at least, is significantly affected by High Temperature/High Shear (HTHS) viscosity. That shouldnt be much of a surprise to anyone since HTHS is what occurs in an engine under operating conditions.

In addition, friction modifiers can play a role. The researchers also blended a series of oils to the same viscometrics (SAE 5W-30) and used four different friction modifiers to study their effects, including a control batch with no FM at all. The results are shown in Table 2.

The conclusions are pretty self-evident. Lowering viscosity improves fuel economy, and friction modifiers have a positive effect on fuel economy as well.

When you talk to heavy-duty OEMs however, they will assure you that its very unlikely that they would specify an SAE 5W-30 for their engines. They do like SAE 10W-30 – but only if the HTHS viscosity remains at about 3.5 cPs. Certainly, friction modifying additives are OK as long as they dont compromise other properties such as soot control, deposit control or antiwear.

Another way to improve fuel economy is to move more cargo. The U.S. Department of Transportation has a pilot program under way in Vermont and Maine studying increased load limits (97,000 vs. 80,000 pounds) as a means of improving fuel use. The thought here is that it takes only an incremental amount of fuel to move the additional 17,000 pounds of cargo, and thus 20 percent more product tonnage could be transported for a rather small amount of fuel.

There are pros and cons to this one. The United States is one of the few countries that limit cargos to 80,000 pounds. Other countries seem to do very well with greater loads. In theory, it would mean that up to 20 percent fewer trucks would be needed on the roads. On the other hand, the additional weight does cause damage to roadbeds, and it would require a lot of work on highways to make this viable. Some have even suggested that a new interstate system be built which would be for trucks only.

Another concern is the fact that heavier loads require greater braking power to stop. There are new brake standards in the pipeline now that will improve the braking capabilities of current trucks. That cant come a moment too soon for me, as the roads where I live (Arizona) have a large number of trucks which seem to be going as fast as I am, and often no more than 50 feet behind me! I shudder to think what would happen if I had to make an emergency stop.

In recent years, the trend has been to use slightly smaller engines (12 to 13 liters, versus 15 or 16L) and lower RPM (1200-1400) to improve fuel economy. If regulators move to raise cargo weight limits, it may be necessary to move back to larger engines and higher RPM. Theres always give and take in every action.

And how will engine oils be affected? Oil marketers are undoubtedly reluctant to have another heavy-duty category change. Every time that happens, costs go up, uncertainty increases and everyone gets nervous. Additive suppliers, who are the ones impacted most by the costs of a category change, will work with OEMs and the various technical groups to make things happen on time – and time is the big factor.

It takes a great deal of time to develop new tests, calibrate them, set limits and get them in place to run the test programs needed to introduce a new category. Common sense and prior history say that the preliminary work has already begun, at least behind the scenes.

Five years is not a long time to get this whole process completed, and so it seems likely to me that we are about to start on Proposed Category 11 (PC-11). Or as they say every year at Indy, Gentlemen, start your engines!

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