School bus fleets operate under extreme pressure and are required to be on time every time to safely transport children to and from school. For this reason, it is vital that each bus runs efficiently and reliably without breakdowns and delays to schedules to keep students safe on their journeys.

Selecting the correct engine lubricant is crucial for this, as the oil protects the internal components of the engine, preventing wear that can lead to unplanned maintenance, breakdowns, and in extreme cases, engine failure.

Consider the Big Picture

For greater efficiency and to enhance the reliability of any fleet, we often need to take a step back to see the complete picture. A crucial part of this picture that can be overlooked is the role that lubricants play in maintaining the efficiency and performance of school buses. High-quality engine oils can improve efficiency by minimizing metal-to-metal contact between moving components and reducing pumping and rotational losses.

Before selecting a heavy-duty engine oil for your fleet, we recommend following these five steps:

1. Consult the Original Equipment Manufacturer (OEM) vehicle manual. This should always be the first step when selecting any lubricant for your fleet. If you need more advice than the manual provides, reach out to the OEM for more information, as they will be able to provide a recommendation based on the engine specification.

2. Consider climate conditions. The location and climate that a vehicle operates in can have an impact on the engine oil’s performance. The temperature ranges for the optimal performance of a lubricant is denoted by its Society of Automotive Engineers (SAE) viscosity grade. Colder average climates may require lower-viscosity lubricants and multigrade oils (those with a “W” designation within the SAE viscosity grade) will ensure protection and efficiency over a broad temperature range.

This is a vital consideration as the SAE grade indicates the oil’s viscosity at both low and high temperatures. The viscosity of the oil determines its ability to flow and move around the engine lubricating the internal components. In cold conditions, if the oil’s viscosity is too high, it may resist movement and delay lubrication, resulting in increased engine wear.

3. Review the benefits of synthetic vs non-synthetic oils. With better stability and improved performance in varied weather conditions, full synthetic and synthetic blend engine oils outperform conventional oils. Full synthetic lubricants also often incorporate unique performance-enhancing additives, which deliver a superior formulation and even greater performance.

4. Seek proof, evidence of performance. Global regulations means that engine lubricants must meet strict criteria, for example American Petroleum Institute (API) CK-4 or FA-4 standards, and proof of this alongside OEM approvals is crucial.

Expert lubricant manufacturers will also provide testimonials and case studies demonstrating their products’ in-service use alongside their own manufacturer test results. These can provide valuable proof of the product’s performance, both in test conditions and the real world. 

5. Ask a lubricant manufacturer for their expertise, support. Leading lubricant manufacturers invest significantly in testing the performance of their product lines so that they can provide informed recommendations for your fleet. Make use of their insight by reaching out directly for their invaluable support and guidance.

Take a Holistic Approach

The wrong engine oil selection can have a significant impact on engine performance and the rate of engine wear. When considering engine lubricants, it is vital to also consider the broader role and impact of lubricants and greases on the entire vehicle.

For example, the vehicle’s drivetrain is an important component that, if neglected, can have a detrimental impact on engine efficiency. By selecting a lubricant based on the OEM’s recommendation, the vehicle can benefit from improved fuel economy. In fact, field testing has shown that an SAE 75W-90 axle gear oil can improve fuel economy by up to 2.25% compared to a SAE 85W-140 oil.

Transmission fluids also play a role in the vehicle’s overall efficiency, so it is also important to select a lubricant in line with the OEM’s recommendation that offers excellent protection and smooth performance through enhanced oxidative stability and anti-wear performance as well as anti-shudder and torque control.

The correct engine oil selection can enhance engine performance and provide it with superior protection. A knowledgeable lubricant manufacturer can support fleet managers in selecting lubricants for their vehicles to improve fleet efficiency and reliability by preventing breakdowns and delays on routes.

Darryl Purificati is the OEM technical liaison for Petro-Canada Lubricants, a HollyFrontier business.