Delivering fuel economy

Fuel economy has become one of the key drivers for hardware and lubricant technology innovation in the automotive market. Now, as the new North American PC-11 heavy-duty diesel (HDD) category introduces a new low viscosity sub-category, there is a much greater need for HDD lubricants to be able to deliver proven engine durability at lower viscosities.

The new PC-11 category is the main topic of conversation in North American HDD engine lubricant circles right now. Here, the timely development of both new and replacement engine tests is a major hurdle that must be overcome if the Engine Manufacturers Association’s proposed first allowable use date of April 2016 stands any chance of being met.

In addition to the significant improvements in oxidation, shear stability, and resistance to aeration, the new category will also address fuel economy improvement.

Two PC-11 sub-categories

For the first time the PC-11 category will be split into two sub-categories. The first, PC-11A offers increased engine protection at traditional viscosities, like SAE 15W-40, at 3.5 centiPoise (cP) HTHS (high temperature high shear) or greater. These oils will be recommended by on and off-road OEMs and will be fully backward compatible.

The second, PC-11B, the so called ‘fuel economy grade', is designed to meet the evolving market needs for fuel economy through lower limits of HTHS (2.9 – 3.2 cP) in SAE XW-30 grades. The durability requirements will be the same for all grades to ensure these new fuel economy grades are risk-free.

The fuel economy grade presents a new set of challenges for engine oil formulators as they must ensure low HTHS oils still deliver the same level of engine protection as defined in current API CJ-4 engine tests and also in the upcoming PC-11 engine tests.

PC-11 will be split into two categories

Infineum has been working on the development of fuel economy HDD lubricants for many years. In that time we have collaborated with OEMs, lubricant companies and academia to model the fundamental principles of wear and lubricant viscosity.

Insight has regularly published updates on progress, which you can read here. This work led us to develop screener tests that can effectively discriminate between good and poor performing oils, and eventually culminated in the validation of the wear protection and fuel economy performance of candidate oils in engine and field tests.

Screener tests home in on best candidates

Infineum developed various bench and engine tests to assess cam and tappet wear in a number of low viscosity lubricant technologies.

The bench and motored engine tests simulated high speed spinning between the cam and tappet, and the selected candidate technologies were further evaluated in a fired engine test.

These tiered screener tests, enabled different components to be evaluated extensively and the best technologies, which provided excellent cam and tappet wear properties at low HTHS viscosity, were successfully identified.

Screener tests showed performance discrimination on cam and tappet wear

Field testing confirms performance

In 2012, a field test programme began on a 3.0 HTHS SAE 10W-30 oil. 13 long-haul trucks with 2007 Cummins ISX engines were deployed on a 500,000 mile test. Four of the trucks used the low viscosity oil and the rest were filled using market leading SAE 15W-40 oils to provide a reference.

Used oil analysis is recognised as a good indicator of engine wear. Iron, which is found in many parts of the engine including cylinder liners and camshaft lobes, gives a good estimation of the overall wear in the engine. Lead, which is used in bearings, is a good indicator of wear or corrosion in this part of the engine. Lastly total base number (TBN) is a measure of the engine oil alkalinity reserve, with a higher TBN indicating a good ability to reduce corrosive acids over an extended period of time.

Analysis of the used Infineum SAE 10W-30 candidate oils showed similar iron and lead levels compared with the commercial SAE 15W-40 reference oils. TBN data for the low viscosity oils showed equal or better TBN retention than some of the reference oils.

These results give a clear demonstration of the wear control provided by the new Infineum PC-11B technology platform.

Iron is a good indicator of engine wear, the Infineum low viscosity oil had Fe levels similar to the commercial SAE 15W-40 reference oils Enlarge view

A second low viscosity package, formulated as an SAE 5W-30, has also been tested in a Cummins ISX engine in the field. Engine rating results from this test showed that the Infineum candidate gave similar wear and sludge results to the market leading SAE 15W-40 reference oil.

Even lower viscosity

HTHS for PC-11B is expected to be between 2.9 to 3.2 cP. The Infineum candidates with HTHS of 3.0 cP lie well within the PC-11 range, and they have demonstrated wear control in both screener tests and in extensive field trials.

The next phase of the project was to lower the HTHS even further and pass API CJ-4 engine tests with an oil with HTHS of 2.6 cP. Infineum is applying the knowledge gained from the performance of these low viscosity lubricants, and is now testing oils with even lower HTHS levels.

Infineum technology has demonstrated excellent wear control at 3cP HTHS, the next phase was to further test the 2.6 HTHS oil Enlarge view

By examining the critical areas of fuel economy in HDD engines and learning how to maintain engine durability in a low viscosity regime, Infineum has been able to develop effective low viscosity HDD engine oils. The new additive platforms for PC-11 will offer the ability to cover multiple viscosity grades to suit the diverse needs of the market, and are supported by years of fundamental research and extensive testing experience.

Click here to read our latest update on the new North American lubricant categories.

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