Optimize Durability and Protection Through Regular Fluid Changes

Heavy-duty and off-highway vehicles work hard for their living, often in challenging conditions, and represent a significant investment for their owners and fleet operators. Correct servicing and maintenance is, therefore, paramount – as is using the right lubricants and fluids to keep all their mechanical systems and machinery operating to optimum levels.

Mark Brighty, a field test engineer at Lubrizol in Hazelwood, Derbyshire, talks about the importance of fluid changes, and of using the best-quality and most suitable fluids.

Regular fluid and filter changes are essential to keep hard-working machinery performing efficiently.

Q: Describe Lubrizol’s field testing. Why is field testing so important to the industry?

MB: Our customers expect the best from Lubrizol’s products, and field testing is one way that we can offer proof of performance. My role is looking after driveline and industrial fluid tests, real-world testing out in the field. Most large manufacturers require stringent approvals for fluids to meet the specification required for their components and in many cases, fluid manufacturers need to undertake field tests for accreditation. A lot of off-the-shelf fluids that are available state “meet the requirements of.” This is where the fluid manufacturer has done their own test work, but it’s not actually been through the formal approval process.

Lubrizol’s field tests are vigorous and we follow original equipment manufacturer (OEM) approval protocols. Samples of used oil are taken on a regular basis, and we analyze those in our laboratories. We look at the fluid as a whole and evaluate the condition of the additive package, the amount of wear metals in the fluid and the condition of the base oil, plus many other different aspects to ensure that the fluid still meets the required performance levels.

Lubrizol provides product differentiation with various techniques that can allow us to monitor vehicle data, vehicle performance, fluid temperatures and efficiency. Whether we are testing on chassis dynamometers or on a proving ground, we can apply telemetry to the vehicle or specific components to measure performance gains or losses over given work/drive cycles. The Lubrizol field testing team can engineer evaluations to get the most accurate data possible, which gives our customers confidence that the fluid can perform as required, as promised, every time.

6 gear automatic transmission & converter

6 gear automatic transmission & converter

Q: Why are transmission fluid changes so important? What happens if they are not done correctly?

MB: Transmission fluid changes can be more complex than a traditional engine oil fluid change. Within a transmission, there can be a lot more components with complex oil ways and galleries where the fluid and contaminants can build up when they are not drained correctly. It becomes even more important to change out the old fluid to avoid poor performance and damage to the hardware.

Of course, filters need to be changed regularly and you need to ensure the drain is done in accordance with the OEM guidelines in the maintenance handbook. If it is not done correctly you can over/under fill the component with fluid, which can have serious effects. You can also cause damage to components by not draining them correctly. For instance, when you drain an automatic transmission, some torque converters have protocols to follow to ensure effective draining. If the old fluid is not completely eliminated, you won’t get the full benefit and protection from the new fluid.

Regular fluid maintenance is all about getting rid of the used oil and contaminants. With engines, these can be by-products of combustion, which can cause acid build-up. In a transmission, following maintenance schedules is important. Some of the wear metals can cause slippage of the synchronizer rings, which impedes gear selection; it can also affect the cooling and protection properties of the fluid, which can be catastrophic. Contaminants can also cause sludge build-up on components, which hinders performance. As machinery is used, you can also get small amounts of water and dirt ingress through breather mechanisms and, in some cases, bypassing seals. If you do not flush these contaminants from the system, eventually they start to clog up and bind to each other like a sludge. Sludge can become hard; with high levels of contaminants, the detergent and anti-wear additives become less effective and the fluid fails to work effectively.

Q: What are the benefits of proper, regular fluid changes?

MB: Planned routine maintenance is better than costly repairs. It’s cheaper in the long run to change your oil and filters regularly than it is to spend a lot of money on a new transmission. Planned preventative maintenance is key to good fleet practice, but it also maintains efficiency: when the wheels aren’t turning, you’re not earning.

In a transmission, the anti-wear and detergent properties of the fluid work hard because the gears are meshed tightly together and are heavily loaded; the fluid creates a boundary layer (a thin layer of fluid and protective additive chemistry) between the two gear teeth and stops them from touching, reducing wear and prolonging the life of the components.

Q: How can you tell if you are in need of a fluid change? What kind of warning signs might you see?

MB: In some transmissions, indicators can be severe and in others, less noticeable. A diligent owner/mechanic will spot the signs more quickly and can avoid failures. In a transmission, you may notice poor gear engagement. With automatic transmissions, you may get poor speed transfer from the engine to the transmission if the torque converter is not operating efficiently. If the fluid has carbonized, creating a tar-like substance, the torque converter may not spin freely, creating a disconnect from the engine. Ultimately, a fluid which is not working correctly will cause failure. Some of the more noticeable indicators of failure may be whining from bearings, grinding of engagement teeth when changing gears and ultimately metal fatigue, which is generally seen when metal filings are observed in the drained fluid. Metal filings are not a good sign; fatigue on gear teeth surfaces can cause severe damage and require a transmission to be rebuilt with new components at high cost.

Fluids naturally have an aroma about them. However, if a fluid is under strain it can become oxidized, giving it a burnt smell. This can also lead to the fluid becoming more viscous, making it harder to pump around. This gives the components less protection and leads to premature failure. Color alone is not an indicator that the fluid requires changing. This is why at Lubrizol, when we manage our field tests, we analyze the sample for many different things to ensure the integrity of the fluid throughout the test.

Many new vehicles now have oil condition monitoring; electronic sensors send information about engine revolutions, temperature and driving time to the car’s computer. Complex mathematical algorithms then predict the level of oil degradation which has taken place. When this reaches a preset limit, it triggers a warning light informing you that the vehicle requires an oil change or service. This service indicator light comes on well in advance of the fluid actually failing, allowing you to change the fluid and keep the vehicle running at its optimal level. Some tractors are fitted with suction filters. The pump pulls the oil up out of the sump of the transmission, and it passes through the suction filter which is fitted with oil pressure sensors before and after it. If the oil pressure after the filter becomes too high, the filter is becoming blocked. This triggers a warning light to tell the driver to change the suction filter. This generally occurs due to contamination from dirt ingress.

Q: How frequently should fluids be changed?

MB: Fluid drain intervals are generally calculated by the vehicle manufacturer and are indicated in the maintenance manuals according to the fluid type, the running conditions and the usage. With trucks, for instance, it’s dependent on what fluid you are using. You could expect to change transmission fluid from every 60,000 km up to 500,000 km, depending on oil grade/specification, topography and environment. If you put a lower-grade, lower-quality fluid in, you’ve got to change it more often because it can’t stand the arduous conditions and life cycle. If you use a higher-specification fluid, you may be able to run the vehicle up to 500,000 km without an oil change.

Q: So what distinguishes the higher-quality fluids?

MB: Higher-quality fluid can be distinguished in various ways: improved fuel economy, longer drain intervals, improved durability and better thermal stability. Poorer-quality fluids generally do not have the best additive packages or concentration (treat rate) of additives that provide protection for wear, cleanliness and efficiency; they don’t give as much protection to the gears against things like water and dirt ingress. The treat rates are a lot lower, so the additive package will not be as robust. If you use a lower-specification fluid you need to change it more often, which means your vehicle may be off the road more often.

Q: And how about fluids formulated for external factors such as temperature and climate, or for certain operating cycles?

MB: Multigrade oils stay close to the optimal viscosity over a range of temperatures — not too thick when it is cold and not too thin when it is hot. Some fluids are developed for environmental factors; countries with higher average temperatures have little need for winter grade fluids designed for colder climates. Topography is also a big issue. When driving in arduous conditions, pulling really high loads, you want a transmission fluid that’s got a higher viscosity. However, you do not want to compromise efficiency. With more stop-start applications, you need a fluid that is less viscous, as it does not get hot and become thinner. However, you do not want to compromise durability. It’s not necessarily going to get as hot, but it needs to remain viscous enough so that its pumpability remains stable. If you’re doing long haul, you also want a fluid that’s going to give the best efficiency. However, working in severe conditions, efficiency is not as paramount as durability. You want a fluid that gives protection for your gears and other components.

Part 2 of this series examines the specifics of determining fluid change intervals and procedures that should be followed.