- Machine Engines: All
Introduction
Caterpillar engines that are operated at high altitudes are severe duty. In order to optimize engine life, adjusting engine oil maintenance schedules and using a high quality oil is recommended. High altitude operation may increase the soot level in the engine oil. Increased levels of soot can cause oil deterioration, deposit formation, and abnormal wear. More frequent oil drains and premium performance lubricants can offset these negative factors.
Altitude
The air at a high altitude is less dense than the air at sea level. The air contains less oxygen at a high altitude. All diesel engines require oxygen for the efficient combustion of diesel fuel. Diesel engines that are operating at a high altitude may experience the following conditions:
- Increased exhaust smoke
- Reduced power
- Increased soot levels in the oil
- Higher exhaust temperatures
- Higher turbocharger speeds
Compensating for Higher Altitudes
A turbocharged diesel engine can compensate for low air density until the engine reaches the exhaust temperature limit or the turbocharger speed limit. Excessive exhaust temperature could result in the following conditions:
- Increased heat load on cooling system
- Reduced engine oil life
- Reduced oil film thickness
- Increased component wear
Caterpillar diesel engines are protected from excessive exhaust temperature and excessive turbocharger speed. The engine restricts the maximum fuel rate at higher altitudes. The altitude capability of an engine is defined as the maximum altitude an engine can be operated at rated power and rated speed without violating the maximum allowable exhaust temperature and turbo speed.
Caterpillar Definition of Altitude
The Caterpillar definition of high altitude varies by the type of engine and family of machine. Some of the Operation and Maintenance Manuals (OMM) use altitude to define normal and safe operating conditions for the engine oil.
At altitudes below 1830 m (6000 ft), a 500 hour oil drain is permitted. For engines that operate above 1830 m (6000 ft), the oil drain schedule is every 250 hours. An oil sampling and oil analysis program is required to extend engine oil drains beyond 250 hours.
Effects on Engine Oil at High Altitudes
There are two concerns for the engine oil at high altitudes. The first concern is increased soot loading. The second concern is increased oxidation.
First, engines that are operated at a high altitude are under severe operation. When you operate at severe conditions, it is beneficial to select premium maintenance products for the engine. The following premium maintenance products are recommended when you are operating the engine in severe conditions:
- Engine oil
- Engine oil filters
- Fuel filters
Premium engine oil contains special additives that are designed to limit harmful wear that is caused by soot. The premium engine oils also contain additional anti-oxidants that limit thickening of the oil and wear. This is caused by oxidation of the oil.
The engine should be placed on an oil change program. A oil change program evaluates all of the factors of oil life and engine life. An optimized oil change program will provide a service interval that reduces the harmful aspects of soot at high altitude and increased oxidation.
Selecting Premium Engine Oil
Engine oil with a high API category rating is the best engine oil. CI-4 oils are superior to CH-4 oils. CJ-4 oils are superior to CI-4 oils.
New oil categories provide improved performance over the previous category. Properties such as wear resistance and deposit control are critical to engine life. Illustration 1 shows the improved wear performance of DEO CJ-4 oil when the oil is compared to DEO CI-4. Illustration 1 also shows that a typical CH-4 oil will not pass the valve train wear test limit for the CI-4 category.
 | |
| Illustration 1 | g01380337 |
The new oil categories are also designed to handle higher levels of soot, while maintaining a safe viscosity and controlling wear. Illustration 2 shows the succession of soot handling capabilities for the three latest API categories.
 | |
| Illustration 2 | g01380384 |
Caterpillar DEO multigrade oil is always an excellent choice for high altitude operation. Caterpillar DEO oil is formulated as premium diesel engine oil in all areas of measurement and the oil is extensively tested in Cat engines. Cat oil filters and fuel filters are also designed to meet the highest standards for filtration and durability.
Optimizing Oil Changes for a High Altitude
Begin with more frequent service intervals to optimize oil changes. For example, many new machines allow a 500 hour oil drain interval. If the machine will be operating at a high altitude, 500 hours could be too long. The first three oil drains should be done at 250 hour intervals. Take oil samples at each oil drain. Oil samples should be closely evaluated for the following conditions:
- Iron wear
- Soot
- Oxidation
If the initial oil samples do not indicate problems, with wear, soot or oxidation, the oil change can be extended in a 50 hour increment to 300 hours. Evaluate the oil changes for three more service intervals.
Extending oil drains in 50 hour increments is a safe way to optimize the oil change for machines that are operating at a high altitude. A safe stopping point is to use the global Cat Wear Tables. The Wear Tables have three categories for wear elements:
- "No action required"
- "Monitor Compartment"
- "Action required"
Machine engines that are operating near sea level will usually be within the no action required range. For engines operating at a high altitude, with elevated soot levels, the wear elements can be allowed to rise into the monitor compartment range.
As stated earlier, soot levels at a high altitude will be higher. Soot values could exceed 60 UFM (150% Allowable) in some cases. These higher soot values are only a concern if the wear rate increases dramatically. If the wear rate is relatively constant, the soot values should simply be observed and trended.
Consistent maintenance practices are always important to engine durability. For best results, maintain engine oil drains within 25 hours of the target oil drain. Poor maintenance schedules may lead to over extended oil life and abnormal engine wear.
SOS Services interpreters can find additional in formation on optimizing oil change intervals at the SOS Services Knowledge Network site. The document PEDP8025 Optimizing Oil Change Intervals is located within the Data Analysis Guides folder. An equivalent brochure for customer use is PEDP7035.