Low-viscosity, heavy-duty diesel engine oils

R. David Whitby | TLT Worldwide September 2012

Manufacturers are making the switch in new engines for greater fuel efficiency.
 

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OPERATORS OF HEAVY-DUTY, DIESEL-POWERED TRUCKS require engine durability combined with low operating and maintenance costs. In Western Europe and North America, engine lifetimes of more than 1.5 million kilometers before a major overhaul are now common. At the same time, typical oil drain intervals are between 60,000 and 150,000 kilometers, depending on driving conditions and engine load.

Due to the demands placed on heavy-duty diesel engines, many operators have insisted on using 20W-50 or 15W-40 viscosity engine oils in order to ensure adequate engine lubrication and durability.

More recently, with the advent of regulations in Western Europe, North America, Japan and other countries that require improved fuel efficiencies, lower exhaust emissions and emission control system durabilities, attention has been focused on lower-viscosity, heavy-duty diesel engine oils (HDDEOs).

With the rising prices of gasoline and diesel, fuel economy is becoming a more important factor when considering operating costs. Unlike the ACEA A/B and C specifications and the ILSAC GF-5 specification for gasoline and light-duty diesel engines, the ACEA E and API CJ-4 specifications for HDDEOs do not have tests for fuel economy improvement. In 2011 the U.S. Environmental Protection Agency and the National Highway Traffic Safety Administration established a Heavy-Duty National Program, which reduces greenhouse gas emissions and fuel consumption for on-road medium-duty and heavy-duty vehicles. This program will begin with model year 2014 trucks and should be fully implemented by 2018.

Although the European Union has only recently begun discussing fuel efficiency targets for trucks and buses, OEMs are already promoting heavy-duty diesel engines with improved fuel economy. A number of manufacturers recommend lower-viscosity lubricants in their newest engines, recognizing that lower viscosity engine and gear oils have provided demonstrable fuel economy benefits for cars and vans.

Some truck operators have begun to make the switch. Data published by Centre Professionnel des Lubrifiants in 2012 indicated that the percentage of 0W, 5W and 10W-30 viscosity grades for HDDEOs in France had risen from 2.2% in 2005 to 4.3% in 2010. Less energy is consumed when starting a cold engine when it is lubricated by a 5W-30 viscosity oil compared with a 15W-40 viscosity oil. Lower viscosity oils also help reduce friction in an engine, which can result in fuel savings.

Many truck operators continue to be concerned about engine wear that could result from using lower-viscosity oils. To help assuage these concerns, Chevron Oronite recently published the preliminary results of field tests using 15 trucks that ran for up to 150,000 kilometers using various viscosity grades of engine oils (1). The results indicate that 5W-30 and 10W-30 oils provide more fuel economy improvement potential than 5W-40, 10W-40 or 15W-40 lubricants for heavy-duty diesel engines. More important, low-viscosity and low high-temperature, high-shear (HTHS) engine lubricants with optimized additive technology and viscometric properties provide long drain capabilities and wear protection in combination with fuel economy improvements.

Lubrizol, Afton Chemical and Infineum have also developed additive technologies for low viscosity HDDEOs. Lubrizol claims that its CV9601 additive package enables the formulation of low viscosity 5W-30 heavy-duty diesel engine oils with 3.5 HTHS, which ensures durable protection while delivering real- world, measurable fuel economy gains. CV9601 is backed by global specifications and a battery of extreme field and bench tests. Shell, Castrol, ExxonMobil and other leading suppliers of lubricants are now promoting 5W-30 viscosity HDDEOs.

The only task now for lubricant marketing companies is to persuade truck and bus fleet operators that the fuel economy benefits of low viscosity HDDEOs do not need to come at the expense of higher engine wear, shorter oil drain intervals or reduced engine durability.

REFERENCES
1. “Low Viscosity Lubricants for Improved Fuel Economy in Heavy Duty Engines while Maintaining Lubricant and Engine Durability,” W. Van Dam et al., Paper 5.3, TAE 18th International Colloquium Tribology, Esslingen, 2012.
 

David Whitby is chief executive of Pathmaster Marketing Ltd. in Surrey, England. You can reach him at pathmaster@dial.pipex.com.