Truck Engine Oils

Understanding Fleet Engine Oils

A truck/bus engine oil is an essential item when it comes to the health and performance of your fleet. Choosing the wrong or an inferior product can lead to catastrophic and sometimes irreparable damage to the engine, while on the flipside, a superior oil can extend life, improve fuel economy and overall efficiency. This is extremely important in the everyday operations of your fleet as it is imperative that your trucks are on the road at all times with maximum efficiency and do not compromise on the company’s productivity.

However, as we have seen with automotive engine oils, it can be extremely confusing to decide what the right product is for your vehicles, especially with the complex specifications and terminologies on packaging and data sheets. Terms like “long drain” and “Euro 7 engine oil” might seem cryptic at first glance. Hence, many default to comparing prices to make a choice—a practical short-term solution. However, factors such as drain intervals, downtime reduction, oil capacities, filtration costs, and fuel efficiency demand a longer-term perspective.

For fleet managers, particularly those with in-house service teams, there’s a golden opportunity to explore and select from a broad range of truck engine oil options. Depending on the fleet size, purchasing oil in bulk can be cost-effective while ensuring optimal benefits from top-tier products. 

Before we dive into these options, we always recommend consulting your OEM manual before making any decision as adhering to the specifications recommended by OEM ensures you do not void your vehicle(s)’ warranty. 

European Emission Standards: Steering towards greener roads

The European Union has established emission standards to regulate the exhaust pollutants from new vehicles. These standards are part of a broader initiative to combat global warming and reduce pollutants like CO2. Understanding these regulations is key to selecting oils that not only comply with but enhance environmental efforts.

Understanding the Oil specifications

The European Automobile Manufacturers’ Association (ACEA) sets benchmarks for oil performance, known as ACEA Oil Sequences. Updated every four years, with the latest (E8 & E11) in 2022, these guidelines categorise heavy-duty engine oils with an “E” prefix. Each category underlines specific properties and applications, crucial for making informed decisions about engine oil.

We will look at these categories below:

E4

Considered “stable” the key characteristic of E4 oils is their emphasis on a high level of detergency, reducing the build-up of combustion deposits on pistons and excellent control of cleanliness. Although they are not low-SAPS oils and are not recommended for vehicles with DPF, E4 products usually have either partially- or fully-synthetic oil or at least, the very highest-rated (group III) mineral oils. For this reason, E4 oils would be more expensive than your regular mineral based formulations.

E6

Ultra-high-performance diesel lubricants (UHPD), E6 lubricants are specifically designed for use in long drain applications operating in severe conditions. Very similar to E4 engine oils, E6 has the extra benefit of low-SAPS for vehicles that have a DPF and are usually fully synthetic. They are considered top-performing oils but are usually the most expensive type of engine oil. Many of these oils can also provide fuel economy benefits. E6 spec has now been replaced with E8. 

E7

An oil that suits the majority of current engines as long as they do not have a diesel particulate filter (DPF) in their exhaust. Usually a mineral based engine oil they would be cheaper than low-saps oils. These factors make it one of the most popular sequences in the Irish market today.

E9

These oils are extremely similar in application to E7 oils, but with one important exception – they have tight limits for sulphated ash, phosphorus and sulphur. They are considered low-SAPS oils and are designed specifically to suit trucks that are built with a DPF in the exhaust: low-SAPS oils produce less ash when they burn, so the DPF needs cleaning less frequently.  Although still mineral-based, E9 oils need a low-sulphur base oil that differs from the group I base oil used for E7 oils, which would make E9 more expensive than E7. These were recently replaced with the new E11 spec.

E8 

ACEA E8 oil category sets high standards for motor oils, requiring them to maintain consistent performance, keep engines clean, and effectively manage soot and contaminants. Oils in this category are designed to offer outstanding anti-wear protection and maintain their stability throughout the entire oil change interval. Specifically formulated for EURO VI engines, E8 oils are also compatible with older EURO models (I through V), supporting extended drain intervals. It’s crucial to adhere to the manufacturer’s recommended oil change schedules.

E11 

Building on the E9 standard, this high viscosity-index category prioritises piston cleanliness and imposes stringent limits on factors contributing to bore polishing. The specification is focused on minimising wear, managing soot effectively, and neutralising contaminants. Oils conforming to this standard are optimised for diesel engines in demanding heavy-duty environments. They are compatible with EURO VI engines and maintain backward compatibility with EURO V through EURO I engines, promoting extended drain intervals.

Manufacturer Specifications

To make things difficult, truck manufacturers also have their own unique oil specifications that run parallel alongside the ACEA’s sequences. For example, many E7 oils have Renault RLD-3, Volvo VDS-3 or MAN M 3275. Similarly, E9 oils can often meet Volvo VDS-4 and Mercedes 228.51 specifications

The majority of premium high-performance oils are so well formulated that there are specific areas area where they will overlap. For example, many E6 oils also meet E4 and E7 specifications and have a number of manufacturer approvals. This is particularly useful for operators of a mixed fleet where there is a potential of using the wrong oil.

What are LOW-SAPS engine oils?

Diesel Particulate Filters (DPF) greatly affect the type of engine oil that can be used in your fleet. When combustion process in an engine occurs, a small amount of oil is burned off. The parts of the oil that are burned off could quite quickly clog a DPF, which could cause numerous issues. This is why low-SAPS or low-ash oil is needed.

So, if your truck has a DPF, your engine oil choices fall to either an E9/E11 or E6/E8. Again this will be decided by what the OEM manufacturer recommends as the most suitable oil for your engine.

Drain Intervals: A Key Cost-Saver

Longer drain intervals are a huge benefit to fleet operators. Downtime is reduced and a number of costs drop as service periods decrease along with labour costs. But what factors influence drain interval periods? Most manufacturers approximately 60,000-70,000km operating within Ireland, reduced to 30,000-40,000km in severe environments such as short distance urban or construction work but extended to maybe 80,000-100,000km on long distance and lighter duties. Fuel consumption can be a good indicator when it comes to drain intervals. Higher than average fuel consumption would usually align with tougher demands on the oil.

One of the main factors restraining oil life is oxidation. This is the gradual acidification and degradation of the oil; new oil is alkaline in order to combat the acidity of the combustion. Once an oil’s reserves of alkalinity are severely depleted it’s ability to resist engine wear is also depleted. Taking oil into this danger zone by delaying a change is risky, but many fleet managers take it due to the perceived savings on oil changes. Semi- and full-synthetic base oils are better at fighting oxidation than mineral base oils, explaining why truck manufacturers specify that synthetic-based E4 and E6 oils are essential if operators want to take drain intervals out to the maximum, sometimes as high as roughly 120,000 km under the right conditions.

Typically, synthetic base oils have a much higher viscosity index than mineral oils. That means they are more resistant to thinning at high temperatures and to thickening at low temperatures. They are able to retain this characteristic longer than mineral oil with added viscosity improver. Consequently, they stay closer to their original viscosity for longer, stretching their usable life.

It is up to the operator to calculate whether longer drain intervals validate the premium cost for E4 and E6 oils, taking into account the savings on filters too. As a rule, extended drain intervals only make real sense if they delay the change by at least one scheduled safety inspection.

The Importance of Oil Analysis

When first attempting to extend oil drain intervals, it is essential to use some form of oil sampling to verify how far it is safe to go. Sampling will highlight a number of areas regarding oil life, including how much oxidation has occurred, as measured by the TBN (total base number). Other than planning maintenance operations Oil analysis has a number of benefits including:

• Reduce operating costs
• Anticipate and plan maintenance operations
• Increase equipment lifespan
• Improve equipment reliability and performance
• Optimise oil change frequency

How Much Oil is consumed in Modern Engines?

Oil consumption of around 0.075 per cent of fuel consumption is estimated to be typical for a modern heavy-duty diesel engine. A comprehensive approach to engine-oil management includes monitoring the daily use of top-up oil in order to spot engines that are over-consuming or unhealthy. But first, we need to identify what is considered regular oil consumption? Euro-1 engines of 20 years ago regularly would use up oil of between 0.1 and 0.15 per cent of their fuel consumption, even in optimum condition.

But burnt engine oil is a source of exhaust particulates so vehicle manufacturers have worked hard to regret a hold on consumption in order to comply with increasingly stringent and demanding emission limits, especially as climate control becomes a bigger issue. Healthy Euro-4 and -5 engines on average should consume oil at a rate no greater than 0.075 per cent of their fuel consumption. So, for example, if a fleet consumes 100,000 litres of fuel each month, top-up oil used in the same period should not average out at much more than 75 litres unless there is an extraordinarily high amount of older trucks.

Fuel-Economy Engine Oils

Operating conditions and cycles are a major influence on the cost-effectiveness of low-viscosity oils designed to save fuel.  But some fleet managers think in the short term and see that these fuel-efficient oils can cost up to 2 or 3 times as much as mineral oil. Therefore, it is of utmost importance to be able to explain and highlight, firstly, how fuel economy engine oils work and, secondly, the long-term benefits to both your oveall costs and your fleet.

The improvement in fuel economy is mainly created from a reduction in viscosity. Thinner oil offers less viscous drag and is circulated around the engine quicker during a cold start, reducing friction and wear immediately. Traditionally, the SAE viscosity rating for diesel engines in trucks had been an E7 15W-40. On the other hand, fuel-efficient oils are usually 5W-30 and feature synthetic base oil. The 5W part of the highlights that the oil will stay thin in low temperatures, helping with cold starts. The 30 shows that it will also stay thin at high temperatures compared to a 15W-40.

Because the engine spends the majority of its time operating at hot temperatures, the second number in the viscosity rating has a greater influence on fuel economy. The limiting factor is that vehicle manufacturers refuse to sanction oils that are too thin at high temperatures. Thin oils leave a thinner film on wear surfaces such as camshafts and bearings: if it is too thin the film shears. Synthetic base oils have a specific formulation that gives them greater film strength compared to mineral oils operating in these high temperature, high shear (HTHS) conditions.

This need for adequate engine wear protection at high-temperatures means ACEA sequences include an HTHS viscosity limit that effectively restricts oil to high-temperature viscosity ratings to no lower than 30 for fleet engines, capping the fuel efficiency potential at typical operating temperatures. Fixing viscosity at high temperatures puts the emphasis on low-temperature viscosity. Going lower helps here, too, but the net benefit naturally is dependent on the frequency and need of cold starts, which would be extremely rare in countries such as Ireland.

All this explains why the economic benefits of fuel-efficient 5W-30 oils are variable but advantageous. Economy gains of 2.0 to 4.0% are normally quoted: not all such oils are created equal, and much depends on the baseline used for comparison. Gains are highest in percentage terms when a vehicle is stationary with the engine idling because there are no aerodynamic or rolling resistance losses, so a reduction in engine losses counts for more. Low ambient temperatures and cold start naturally enhance the benefits of thinner oil.

There are many variables to be considered when deciding to switch to a fuel economy oil. It is extremely important to remember that today’s engines have a wide range of needs when it comes to lubrication. Again always consult your owner’s manual or speak to the OEM manufacturer to find out not only the suitability but the expected performance levels when it comes to the right engine oil. Taking a risk when downtime is the biggest cash flow leakage means that using the right engine oil and lubricants, in general, is essential.

TotalEnergies Rubia Range

As we have seen, commercial vehicles are faced with extreme driving conditions on a daily basis in an industry where downtime is detrimental in regards to operating costs. Chosen by OEMs, Global Partnerships and long-lasting co-operation with major truck manufacturers across the globe, the Rubia brand has earned a reputation for quality and reliability. OEMs put quality and brand re-assurance at the heart of their purchasing decision.

All Rubia engine oils are manufacturer-approved, meet the needs of multi-vehicle fleets, and are designed to comply fully with the ACEA and API specifications and environmental demands of the latest generation of diesel engines conforming to EURO I, II, IV, V and VI including EGR, SCR and DPF engines.

TotalEnergies has close partnerships with major truck manufacturers around the world and develops high specification lubricants that fulfil the needs of today’s heavy-duty commercial vehicle sector, while also researching and developing innovative new products that will cater to the needs of this sector in the future.