How to Optimize Oil Change Intervals in Heavy-Duty Vehicles

1. Engine Design, Age and Conditions – Engine design characteristics and numerous running conditions can affect oil life factors from exposures to contaminants and other conditions.
2. Driving Patterns and Conditions – Where and how the truck is driven.
3. Oil Properties – Quality and formulation performance of the engine oil.

Engine fuel efficiency is perhaps the most directly correlated factor to the life of the engine oil. It is improved by combustion efficiency, which can determine the type and amount of particles that are blown by the piston rings. Piston “blowby” is usually the primary source for ingression of contaminants into the oil.

This can include dirt, water, soot, fuel, nitrogen oxide (NOx) and partially burned hydrocarbons (HC). Not only does the combustion efficiency play a role, but other engine design factors such as seal efficiency, temperature control and emissions control methods influence the type and concentration of contaminants in the oil.

Some measureable engine characteristics such as total operating hours and mileage are unavoidable and will likely lead to a shortened oil drain interval. However, maintaining a healthy oil-flow system is manageable by consistently providing sufficient filtration and seals.

In critical components such as filters, the failure mode does not stop with merely a shorter oil life when subpar conditions are experienced. Figure 1 shows how poor filtration can produce a chain reaction of damaging effects on the engine as well as higher operational costs.

Filtration is the counter to contamination. Therefore, it is important that the dirt-holding capacity of the filter be in-line with the anticipated or needed oil drain interval.

In addition to filtration and seals, another engine characteristic that has an effect on oil drain intervals is the oil capacity or sump size. Basically, with an increased volume of engine oil circulating within the engine, there will be a decrease in contamination concentration. Larger sump size also means more oil additives and less thermal distress. As a result, engine manufacturers that offer the largest sump size generally allow for the industry’s longest recommended oil drain interval.

While all engines are designed to provide healthy conditions for the oil to flow, even the best designed models have some level of anticipated contamination over time, either generated from internal or external sources. Consequently, it is the responsibility of the truck owner to ensure that optimal maintenance and healthy conditions are stabilized.

The conditions an engine oil must endure are reflected in the conditions the truck encounters. Driving in extreme temperatures, for example, is not a healthy environment for the engine oil. On the one hand, cold starts can cause the oil to thicken, which can impair bearing and cylinder wall lubrication at start-up. On the other hand, high heat environments will not only lead to a drop in viscosity but can also result in harmful chemical reactions such as oxidation within the oil and shorten oil life.

Additionally, severe external conditions like dirt roads and high air humidity increase the probability that these airborne contaminants will invade the oil, usually by way of the air intake and through the combustion chamber.

While engine oil has the potential to become contaminated by several external conditions, any factor that influences fuel efficiency also affects the life of the oil. Lower fuel efficiency implies that your engine is not operating at an optimal state, which forces it to work harder. As a result, your engine oil is also working harder. Some of these fuel-efficiency factors include steep roads, high loads, stop-and-go driving, lugging and even the style of driving.

Diesel engine oils licensed by the American Petroleum Institute (API) and the European Automobile Manufacturers Association (ACEA) are formulated to provide the best engine-protecting properties and to deliver the longest service life possible.

However, even the highest quality oil can be challenged by a range of factors that escalate its own degradation. Not only are the initial conditions (cleanliness, age, etc.) of the engine oil critical but also whether the right performance grade of engine oil is selected to counteract the stressing conditions and exposures that can shorten an oil’s life.