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Best Oil Viscosity for Fleets, Diesel Engines & Equipment
Key takeaways:
- Oil viscosity determines how lubricants perform in different conditions. Thicker oils (higher viscosity) protect better at high temperatures, while thinner oils (lower viscosity) flow more easily in cold starts.
- 10W-30 synthetic or synthetic blend is now the preferred choice for fleets, diesel engines, and equipment, replacing the older 15W-40 standard.
- Selecting the correct viscosity requires considering OEM recommendations, engine design, operating conditions, and oil formulation type.
Viscous fluids flow more slowly than those that are less viscous, but how does this impact your machinery?
The guide below explores the best lubricant viscosity for these applications based on extensive industry research and real-world results. We’ll also cover how lower-viscosity synthetic oils can be a more cost-effective option that still delivers superior performance.
What Is Oil Viscosity?
Oil viscosity, otherwise known as oil weight, describes the speed at which a particular oil moves and is often used to compare it to other lubricants. An oil with greater viscosity is thicker than one with lower viscosity, which flows faster.
The Society of Automotive Engineers (SAE) classifies oil viscosity using two numbers separated by a “W.” The number before the “W” indicates viscosity at lower temperatures, while the second number describes the oil’s viscosity when the engine has reached its normal operating temperature. For example, a 5W-30 oil has a viscosity of 5 at colder temperatures and 30 at operating temperature.
The SAE measures oil viscosity at these two temperature points to aid in comparing oils based on the intended operating environment.
For instance, if you live along the East Coast, you’d likely want to choose an oil that’s less viscous at lower temperatures to protect your engine. If you live in Arizona or Nevada, you probably want an oil that’s more viscous at higher temperatures to keep metal components from scraping one another.
What Is the Best Oil Viscosity for Fleets, Diesel Engines, and Equipment?
A full synthetic or synthetic blend 10W-30 motor oil offers the best oil viscosity for diesel engines, fleets, and heavy-duty equipment. The previous standard was 15W-40, which typically offered the best year-round performance in normal operating conditions.
However, many in the transportation industry have since switched to 10W-30 as the standard because it offers the following benefits:
- Performs across a wide range of climate conditions without sacrificing performance
- Reduces costs because it’s more readily and widely available
- Suitable for multiple vehicle types and operational loads
- Synthetic formulation extends performance across longer service intervals
Because changes in modern gasoline and diesel cannot do it alone, automotive manufacturers have redesigned their engines to help achieve mandatory emissions thresholds. With this evolution comes the need for enhanced lubrication.
When combined with the latest engine designs, superior lubricants can help improve fuel economy by introducing greater mechanical efficiency.
Why Are Synthetic Blends and Full-Synthetic Oils Best for Fleets, Diesel Engines, and Equipment?
Synthetic oil offers superior performance over conventional oil, resisting sludge formation and deposit build-up. The additive formulations within synthetic oils perform better in extremely hot and cold temperatures. These oils are best for on- and off-highway fleets, as well as agricultural applications.
However, synthetic oil may not be as cost-effective for fleets, especially those that are smaller or just starting. Synthetic blend oils offer a more affordable solution. Striking a balance between costly synthetics and short-lived conventional oils, synthetic blends combine the performance of a synthetic with the cost of a conventional oil.
How To Choose the Best Oil Viscosity for Your Fleet
The first thing you should do when selecting the best oil viscosity for your fleet is consider OEM recommendations, which are often listed in the owner’s manual. Most modern fleet vehicles, diesel engines, and heavy-duty equipment require synthetic blend or full synthetic oil to match the engine’s design and performance. However, remember that these recommendations are often based on average operating conditions and may need to be adjusted accordingly.
Also consider the engine type, age, and mileage. If you go by the American Petroleum Institute’s (API) service categories, note that CK-4 is backward compatible, but FA-4 is not. For diesels, ensure the oil viscosity remains compatible with the Selective Catalytic Reduction (SCR) system to avoid complications with this part of the emissions system.
Brand reputation also plays a significant role in the oil viscosity you choose. Working with a trusted supplier like Cadence can help you identify quality products, ensure quality delivery, and benefit from years of industry expertise.
Common Mistakes When Selecting Oil Viscosity
The proper oil viscosity keeps fleets, diesel engines, and heavy-duty equipment running smoothly. Yet, small mistakes can just as easily drain resources by reducing engine life, increasing fuel consumption, and leading to costly repairs.
Review these common pitfalls to make smarter lubrication decisions for your company and equipment:
- Ignoring OEM recommendations: Not only will dismissing OEM recommendations likely void your warranty, but you’ll also potentially put your equipment at risk of premature and catastrophic failure.
- Choosing too thin/thick an oil: Too thick an oil can cause poor performance and decreased fuel efficiency, while too thin an oil can increase wear on critical components.
- Overlooking the operating environment: Failure to consider operating conditions, like climate, duty cycles, and load, can cause inadequate lubrication and equipment breakdown.
- Mixing oil grades: Combining two oil grades can deplete both of their additive loads and alter lubrication properties in a way that harms the equipment.
- Sticking with the same oil throughout the machine’s life: Aging engines require oils with more potent additive packages to maintain their longevity.
Selecting the proper oil viscosity is more than just a science; it’s a key part of maintaining your equipment. Avoid these common errors to keep your engines healthier, simplify maintenance, and improve operational efficiency.
However, if you plan on switching to a different viscosity oil, Cadence’s oil analysis services can help ensure you select the best one for your application.
Maximizing Engine and Equipment Life with Proper Oil Selection
Fleet vehicles, diesel engines, and heavy-duty equipment all require proper oil selection, regardless of the industry they operate in. If you’re unsure about which oil viscosity best suits your application, call us at 336-629-2061. Our experts can help connect you with superior lubricants from trusted brands known for their exceptional performance.
FAQs
What does oil viscosity mean?
Oil viscosity refers to how thick or thin an oil is and how quickly it flows. It’s measured using SAE classifications such as 10W-30, where the first number indicates performance at cold temperatures and the second number at normal operating temperatures.
What is the best oil viscosity for fleets and diesel engines?
A full synthetic or synthetic blend 10W-30 is widely considered the best option for most fleets, diesel engines, and heavy-duty equipment. It delivers reliable performance in a variety of climates, lowers costs, and helps improve fuel economy.
Why choose synthetic or synthetic blend oils over conventional oils?
Synthetic oils provide better protection in extreme temperatures, resist sludge and deposit buildup, and extend service intervals. Synthetic blends offer a cost-effective middle ground for fleets balancing performance and budget.
Sources:
Conventional Oil — Sources — Student Energy | Student Energy