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Prime Mover Magazine

Slow burn

Slow burn

Commercial road transport has taken a more conservative approach to embracing lower viscosity lubricants than the automotive industry. With diesel engine oils now trending to thinner viscosities, SAE 30 grade engine oils like Shell Rimula Ultra 5W-30 offer solutions developed from the latest technology for fleet managers determined to reduce fuel burn and increase efficiencies across their trucks.

Each European emissions standard has produced increasing demands subsequent to the previous in which permitted levels of Particulate Matter and Nitrogen Oxides (NOx) have been reduced to the point that they are now scarcely tolerated. Euro 6, the latest standard for heavy vehicle emissions, might be said to represent something of a tipping point for combating particulate matter and nitrogen oxides expelled by heavy vehicles.

As a result the focus has since shifted from particulate matter and nitrogen oxides. Carbon dioxide now finds itself in the crosshairs given that it is recognised as a reducible emission, more so than a pollutant, commonly associated with costly fuel burn.

Original Equipment Manufacturers (OEMs) have since recognised that increasing fuel efficiency across the entire heavy vehicle, through improvements in driveline efficiency, aerodynamics and tyre technology, is a necessary strategy to help reduce emissions of carbon dioxide.

Paul Smallacombe, Product Support Engineer, Viva Energy, says losses of energy from the driveline occur mostly from the engine, but will also be influenced by other driveline components such as the transmission. Laboured axles and wheel bearings will also contribute to increases in fuel burn, one of the major considerations for anyone operating a prime mover.

“By reducing the energy losses through those applications, a sizeable contribution can be made to improving the fuel economy,” he says. “Lubricants technology can help reduce energy losses right across the entire driveline.”

The biggest gains in fuel efficiency are made where the highest energy losses will occur: the engine.

According to Paul, the commercial vehicle industry is beginnings to shift away from the more traditional SAE 15W-40 grades of lubricants that have long been in established use.

“Now you’re seeing, in terms of the global picture, a move to 5W-30 grade engine oils,” he says. “Some of the European OEMs are starting to move to SAE 5W-30 grade lubricants and that’s where a product like Shell Rimula Ultra fits into the market.”

Shell Rimula Ultra 5W-30 engine oil meets the specifications of key European OEMs including MAN Trucks and Scania. Uptake for 30 grade oils in North American OEMs locally, however, has been much slower to date, although some US-based OEMs have shown they are willing to move towards a 5W-30 or 10W-30 specification.

Detroit and Cummins, as of yet, have not found a use for it in Australian conditions with the latest in American driveline technology offered by the likes of Freightliner Cascadia and Mack Anthem a couple of years away from entering the Australian market.

Australia also remains a step behind the emissions technology in the US and conservative in contrast to European OEMs according to Paul.

“With the harsh Australian conditions and heavier loads in hot climates there’s understandably more conservatism from some manufacturers regarding the durability and reliability of 30 grade oils,” he says. “Shell has done a lot of work to prove that need not be a concern.”

Excellent durability he says has already been evidenced from development and testing of API FA-4 engine oils, the American Petroleum Institute category formulated to have lower high temperature high shear (HTHS) viscosity, for the benefits it offers in fuel economy for next-generation diesel engines. Put simply, this means that lower viscosity oils can still provide a good oil film, thus protecting metallic engine parts, while still delivering benefits for fuel economy and emissions.

“In any case 30 grade is already here and we will continue to see a move towards that over the short-to-medium term as some of the US manufacturers start to introduce engines meeting newer emissions standards” Paul says. “From a factory point of view, they are not quite there yet in terms of promoting that in the local market.”

While 30 grade oils have been driven primarily by emission standards, one of the tangible selling points for operators, who are looking to reduce the total cost of ownership, is gains promised in fuel efficiency for businesses whose budgets are devoted every year to millions of litres in diesel.

“You only have to reduce that by just one or two per cent and that’s a major victory for your bottom line,” Paul says.

The rest of the driveline has an impact on fuel burn. Eaton Road Ranger type transmissions, according to Paul, which are commonplace in the market, have moved from requiring an SAE 50 grade to a synthetic SAE 40 with their new specification change to PS-386, as they strive for better fuel economy.

American and European OEMs are lowering and optimising viscosities because it has a fuel economy benefit across transmissions.

Paul says similar trends are being seen across axles with synthetic 75W-90s popular as one or more per cent reductions in fuel burn are increasingly sought after.

“Anywhere between one and four per cent might be gained in the engine depending on loads, driving conditions and the drive cycle,” he says.

“Shell found in driveline rig testing that moving from a 15W-40 engine oil to a 10W-30 brings about anywhere between one per cent in high speed and high load driving and four per cent in low speed, low load driving conditions depending on a stop start or on-highway drive cycle. If you factor that across a transport operator buying 10 million litres of fuel a year and you can save them a couple of per cent in fuel economy then that’s significant.”

Lubricant technology has come a long way in the last decade. Much research and development has gone into base oils, including the additive technology by which thinner oils are produced, to ensure that even greater levels of durability and reliability are achieved to those oils developed from the previous specifications.

One concern of thinner oils in the past, however, is that there can be an increase in their volatility as evaporation and therefore, oil consumption, can prove to be an issue.

“As there’s now higher operating temperatures in the engine to get better efficiency there’s more stress on the oil itself,” Paul says. “What a customer may see from that would be increased oil consumption if they had a poor quality base oil in their engine lubricant.”

But as better base oils counterbalance the concern of increased volatility inherent in thinner oils, it can deliver excellent wear protection and cleanliness to help prolong equipment life.

“All oils have a level of volatility it just depends on how volatile they are and therefore how much they will evaporate under the stresses of engine operation,” he says.

Other advantages provided by synthetics can include longer oil drain intervals, better oxidisation resistance and potential for reduced wear. Being less susceptible to thickening, which could affect fuel economy across the oil drain, is another benefit of using a more resilient lubricant.

“By moving to these lower viscosity grades in your engine, transmission and axle it typically means moving to a synthetic type of oil because that provides lower viscosity while maintaining great reliability and durability with less volatility and therefore less oil consumption.”

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