Is it okay to mix different lubricants in a machine?

Problem: I know my machines are always supposed to use the same lubricants they came with, but if I’m stuck with an empty container, will there be any impact if I top up the fluid with another type?

Solution: Lubricants are designed for a specific purpose, then are tested and developed with stringent quality control. During development, they are subject to a wide range of temperatures, pressures and more to determine how they will perform. As a result, mixing lubricants is a risk machine owners won’t want to take, says Diego Navarro, service marketing manager for John Deere.

“When your machine needs more oil, and you simply add any product you find instead of sticking with what’s already being used in the machine, you are instantly changing the formulation,” Navarro says. “This produces a new product that has not been tested, and it can often affect the machine negatively and accelerate wear, as these two lubricants aren’t designed to work together.”

One negative reaction that mixing lubricants can cause is copper generation. Copper comes from bronze, which is an alloy used in many high-pressure systems pumps. If copper is being leached from the pump’s bronze, pump efficiency will suffer, and contamination of the entire system and components also will occur, according to Navarro.

“If excess copper shows up in your oil analysis, you need to determine why the system is generating copper and fix the root problem,” he said.

Another metal to watch out for in your lubricant is iron, says Navarro. It is important to capture iron particles using magnetic filtration, especially for components such as axles.

“Iron in big quantities damages bearings, oxidizes the oil and consumes the additive,” Navarro says. “When you change oils, not all the iron goes out, so it’s important to collect that iron using magnetic filtration.”

For more details on root cause analysis of lubrication problems, see ‘Maintaining Mobile Equipment’ on page 6 of the Winter 2008/2008 issue of Industrial Lubrication, a supplement included with the December 2007 issue of Machnery & Equipment MRO.

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