How to Prevent Abnormal Cargo Temperatures in Refrigerated Trucks Caused by Low Refrigeration Compressor Oil Levels

How to Prevent Abnormal Cargo Temperatures in Refrigerated Trucks Caused by Low Refrigeration Compressor Oil Levels

In cold-chain transportation, many people focus solely on the temperature inside the cargo compartment.

When the temperature rises, people’s first instinct is usually to assume that the refrigeration unit has broken down, the truck doors aren’t closed properly, or the cargo is packed too tightly. But there’s another cause that’s easily overlooked:The refrigeration unit has run out of oil, or the oil level has dropped so low that it cannot operate stably.

Many refrigerated trucks have two fuel management systems.

One system uses oil for the vehicle chassis, which powers the vehicle’s movement; the other uses oil for the independent refrigeration unit, which cools and maintains the temperature inside the cargo compartment. Some models also use a PTO or other power sources, so the actual configuration may vary. Regardless of the type, the core principle of a refrigerated truck remains the same: just because the vehicle is running normally does not mean the refrigeration system will necessarily continue to operate.

For companies engaged in fresh produce delivery, frozen goods transportation, pharmaceutical cold chain logistics, and cross-border refrigerated transport, the cost of refrigeration oil cannot be calculated solely at the end of the month. It is directly related to cargo compartment temperature, transit time, and liability for handoffs.

Why Is the “Refrigeration Oil” in Refrigerated Trucks Often Overlooked?

For fuel management in standard trucks, it is usually sufficient to simply check whether the vehicle can operate normally.

Refrigerated trucks, however, are different. A driver might notice that the chassis fuel tank is still full and assume the vehicle is operating normally; in reality, the refrigeration unit uses a separate fuel tank or maintains its own fuel consumption records. By the time the refrigeration unit shuts down or begins intermittent operation due to low fuel levels, the temperature inside the cargo compartment has already started to fluctuate.

The risk is particularly higher in the following situations:

• During long-distance transport, the refrigeration unit operates continuously for extended periods;
• High summer temperatures and cross-regional transportation place a greater load on the units;
• When vehicles are parked overnight, the refrigeration unit must still maintain a low temperature;
• Drivers focused only on fuel consumption during driving and did not check the refrigerant oil separately;
• Vehicle handoffs occur frequently, and both the outgoing and incoming shifts assume that the other has already inspected the vehicle.

Temperature issues with cold-chain shipments often do not occur suddenly; rather, there are usually early warning signs, but no one has considered the temperature, the refrigeration unit’s operating status, and the oil level together.

To manage fuel in cold-chain vehicles, first determine which fuel tank is involved.

When managing fuel for cold-chain transportation, the first step is not to create complex reports, but to categorize the uses.

Chassis oil: Determines whether a vehicle can arrive on time

Chassis oil is primarily used for vehicle operation. It affects the route, mileage, transit time, and normal vehicle scheduling.

Refrigeration oil: Determines whether goods can be kept at the proper temperature at all times

Refrigeration oil directly affects whether the unit can operate normally. When a vehicle is parked outside a service area, border crossing, or warehouse, the chassis may be idle, but the refrigeration unit continues to consume fuel.

This is why total fuel consumption alone is not sufficient when evaluating cold-chain transportation. With two fuel measurement systems and two different consumption calculation methods, they must be verified separately.

Before departure, we recommend including these three items in the checklist.

Before a cold-chain vehicle departs, drivers or dispatchers do not need to perform particularly complex operations, but it is best to standardize the following three procedures:

1. Has the current temperature in the cargo compartment reached the loading requirements?;
2. Is the refrigeration unit operating normally?;
3. Is there enough refrigeration oil to cover this shipment and any potential waiting time?

The third point is often underestimated.

The shipping schedule indicates 8 hours, but this does not mean the refrigeration unit will operate for only 8 hours. The unit may continue to run due to traffic jams, queues at warehouses, delays at border crossings, or delays in unloading at the customer’s location. Particularly for cross-border cold chain and long-distance fresh produce delivery, the amount of refrigeration oil should not be determined based solely on “theoretical travel time.”

A practical approach is for companies to gradually build up their own reference ranges based on different vehicle models, seasons, cargo temperature requirements, and routes. After driving the same route a few times, they will know roughly how much fuel the refrigeration system will consume for that trip and how much fuel needs to be replenished in advance.

During shipping, don’t wait until a temperature alarm goes off before taking action.

Temperature anomalies are usually the result, not the cause.

When the refrigerant oil level drops too quickly, the refrigeration unit’s operating time is abnormally long, or the oil level continues to decrease even while the vehicle is stationary for an extended period, dispatchers should take note. Although this may not necessarily affect the cargo at this point, it is advisable to contact the driver in advance to confirm the situation.

For example:

• The vehicle remained parked at a highway rest area for a long time, and the refrigeration unit continued to run;
• Vehicles are lined up outside the customer’s warehouse, and the wait time for unloading is longer than expected;
• The chiller’s operating time has increased significantly, but the temperature reduction has not been noticeable;
• The refrigerant oil level is approaching the low mark, and there is still a considerable amount of time before reaching the destination.

These situations do not necessarily indicate equipment malfunctions or driver errors. Verifying the actual transport status first can usually prevent minor issues from escalating into temperature-controlled incidents.

When the temperature rises, what should you check first?

If the temperature in a refrigerated truck rises, you shouldn’t immediately assume that the refrigeration unit is broken.

We recommend verifying the information in the following order:

1. Are the cargo compartment doors left open for extended periods or poorly sealed?;
2. Is the chiller operating normally?;
3. Is there enough refrigeration oil?;
4. Is the vehicle left parked in a high-temperature environment for extended periods of time?;
5. Are the cargo load capacity, ventilation space, and set temperature appropriate?
6. Are there any issues with equipment maintenance or sensor readings?

By aligning these items in chronological order, the issue is usually easier to pinpoint.

For example, if the cargo compartment temperature begins to rise during a certain time period, while the refrigerant oil level was already near the low mark and the vehicle is waiting to unload, priority should be given to checking the refrigerant oil supply and the unit’s operation. Conversely, if the oil level is normal but the doors are frequently opened for unloading, temperature fluctuations may be more closely related to operational procedures.

During shift changes, it is most common for responsibilities to be unclear.

Refrigerated trucks frequently undergo driver handoffs, warehouse handoffs, and dispatch handoffs between different regions.

If only the quantity of goods and the destination are documented during handover—without recording temperature, refrigeration unit status, and refrigerant oil levels—it will be very difficult to determine at which stage any subsequent issues originated.

It is recommended that the following be confirmed during the handover:

• Current cargo compartment temperature;
• Refrigeration set temperature;
• Is the chiller running?;
• Approximate remaining refrigerant oil level;
• Are there any records of refueling en route or any anomalies?;
• Estimated wait time at the next stop.

This information doesn’t need to be lengthy; a standard handover sheet will suffice. The key is to use the same terminology every time so that there is a basis for review later on.

High fuel consumption in refrigeration systems does not necessarily mean waste.

When many cold chain companies see high refrigeration oil consumption, their first instinct is to reduce it.

However, the primary goal of a refrigeration system is to protect the cargo, not simply to achieve the lowest possible fuel consumption. Hot weather, long wait times, and the transport of frozen goods at low temperatures can all increase the unit’s energy consumption.

What we should really be focusing on is whether there are corresponding transportation-related causes for the increase in fuel consumption.

For example:

• The outside temperature is significantly higher;
• Routes or wait times may be longer;
• Lower temperature requirements for the cargo;
• Frequent opening of vehicle doors;
• Changes in equipment maintenance status.

If these factors have not changed significantly, but refrigeration oil consumption remains consistently high for the same route and similar vehicles, it is worth further investigating the unit’s condition, operating practices, or maintenance records.

During weekly reviews, we recommend focusing on these five items

Cold-chain logistics companies don’t need to hold long meetings every day. It’s already very valuable to review the following five items once a week:

1. Which vehicles have significantly higher refrigeration fuel consumption than others on similar routes?
2. Which orders showed abnormal cargo compartment temperatures;
3. What were the operating conditions of the chiller and the oil level prior to the temperature anomaly?
4. Which vehicles consume more refrigeration oil while idling, waiting in line, or parked overnight;
5. Which vehicles require advance scheduling for refueling, maintenance, or inspection?

In this way, fuel consumption management becomes more than just “calculating diesel costs”; it becomes an integral part of ensuring the quality of cold-chain services.

Which companies have a greater need to manage refrigeration oil separately?

This management approach is particularly well-suited for:

• Fresh food delivery fleet;
• Companies that transport frozen foods, meat, and dairy products;
• Pharmaceutical cold chain logistics company;
• Cross-border cold chain and long-haul refrigerated freight companies;
• Refrigerated truck rental companies and third-party logistics providers;
• Transportation projects requiring overnight parking refrigeration.

Even cold-chain companies with a small fleet should implement this. This is because, in cold-chain transportation, a single temperature issue can result in losses that go beyond just a tank of fuel—it could mean the loss of an entire truckload of goods, a customer complaint, or even jeopardize future business partnerships.

Frequently Asked Questions

Do refrigerated trucks always have a separate refrigerant tank?

Not necessarily. Different refrigerated trucks and refrigeration units have different power sources; some use a separate fuel supply, while others are integrated with the vehicle’s powertrain. Before proceeding, you should first confirm the structure of the vehicle’s refrigeration unit and its actual fuel supply method.

There’s still plenty of chassis oil left, so why did the chiller shut down?

If a vehicle uses a separate refrigeration fuel tank, an adequate fuel level in the chassis does not necessarily mean the refrigeration unit still has sufficient fuel. The fuel levels for the vehicle’s propulsion system and the refrigeration unit should be checked separately.

Does a rise in cargo compartment temperature mean there isn’t enough refrigeration oil?

Not necessarily. Frequent door openings, poor door seals, unit malfunctions, high ambient temperatures, and improper cargo loading can all lead to abnormal temperatures. Refrigeration oil is simply one of the items that should be checked first.

How can you tell if a refrigeration unit’s fuel consumption is normal?

We recommend establishing your own reference ranges based on vehicle type, season, cargo temperature requirements, transport routes, and unit operating time. Do not directly compare low-temperature frozen transport in summer with standard short-distance refrigerated delivery.

Can refrigerated trucks manage refrigeration oil even without a stable internet connection?

Regular logging and post-trip verification are possible, but they cannot fully replace real-time remote management. For cross-border trips, remote areas, or routes with unstable network coverage, ensure there is sufficient fuel for the refrigeration system before departure, and establish clear procedures for manual inspections and handoffs.