The Role of Lubricants, Fluids and Fuel Treatments in Commercial Vehicles

The combination of different lubricants and fluids plays a vital role in ensuring the power, protection and performance of commercial vehicles. From engine oil to driveline or fuel treatments, this blog explores the unique functions of each lubricant and fluid, offering Millers Oils tailored solution to contribute to the seamless operation and increased reliability of commercial vehicles.

Engine Oil

Engine oil is integral to any Internal Combustion Engine (ICE) vehicle, providing critical lubrication to internal components. Its primary functions include reducing friction, dissipating heat, managing contaminants, preventing corrosion, and ensuring a consistent seal between moving parts of the engine. The choice of oil depends on the stringent manufacturer testing and the vehicle’s operating conditions. Additives also play a crucial role in enhancing properties like viscosity and wear protection. Millers Oils Commercial Vehicle engine oils, Truckmaster, Multifleet and Maxifleet have been specially formulated to deliver enhanced protection and maximised performance in driving conditions which place huge demands on the engine, including long haul, start-stop driving with heavy loads and in all weather conditions.


Driveline can be separated into two key areas, gear oils for manual gear boxes and differentials, and transmission fluids for automatic gear boxes. Gear oil is essential in the transmission system, lubricating gears and bearings to minimise friction and wear. The selection of gear oil is led by factors such as load weight, operating speed, and temperature. EP (Extreme Pressure) additives can be incorporated to withstand heavy-duty applications, ensuring smooth gear transitions and extending the life of components. Millers Oils has a complete range of gear and transmission oils for use in heavy duty vehicles, providing extreme pressure protection and improving fuel economy for both manual and automatic transmissions systems.


Greases provide lubrication in various components such as wheel bearings, chassis points, and universal joints. The choice of grease depends on factors such as temperature, load, and speed. Lithium-based greases such as Millers Oils PBL are popular for general-purpose applications including lubricating the fifth wheel, while complex thickeners may be used for extreme conditions. Greases also incorporate additives for enhanced performance, such as anti-wear agents and corrosion inhibitors.

Hydraulic Oils

Hydraulic systems in commercial vehicles rely on specialised fluids to transmit power and ensure smooth operation of components such as steering systems, and lifting mechanisms. Millers Oils Millmax hydraulic oil range, possesses excellent anti-wear properties, high thermal stability, and corrosion resistance, ideal for maintaining the efficiency of the cab tilt system.

Fuel Treatments

Fuel treatments are essential for keeping the fuel system clean and efficient. They protect against issues such as fuel oxidation, injector deposits, sludge build-up and microbial contamination. Diesel, which is commonly used in commercial vehicles, is prone to microbial growth, which can clog fuel filters and injectors. Millers Oils Diesel Power ECOMAX fuel treatment is designed to work with all HGVs, providing added lubricity for the fuel system, and adding up to 4 cetane numbers (CN) resulting in reduced wear on components and increased MPG.

Antifreeze and Coolant

Antifreeze and Coolant serves dual purpose in commercial vehicles. Regulating engine temperature by absorbing excess heat, and preventing freezing in cold climates. Antifreeze and Coolants contain corrosion inhibitors to safeguard the engine’s internal components. Maintaining the right coolant level is critical to prevent overheating and maintain optimal engine performance. Millers Oils Antifreeze and Coolants are suitable for manufacturer and industry standard applications, the excellent heat transfer characteristics provide outstanding engine cooling and component longevity.

The diverse range of lubricants and fluids underscores the complexity of commercial vehicles. Oils, greases, fluids, treatments and coolants collectively contribute to the seamless operation and longevity of commercial vehicles. Understanding the specific requirements of each lubricant and fluid helps fleet managers and operators to make informed choices, ensuring their vehicles run efficiently and reliably, with minimal downtime or disruption.

For a complete package of lubricants, fluids, fuel treatments, paired with oil sample analysis, be Protected by Millers Oils. 

Read about Commercial Vehicle maintenance on our blog. 

Read more about vision oil analysis here.