One of our members recounted a story about a switch in hydraulic oils which had a less than ideal outcome. The machines involved are mining-size hydraulic excavators.

These diggers were delivered to the end-user filled with the machine OEM’s own branded ISO VG46 hydraulic oil. This oil features a zinc-free, anti-wear additive package and has a viscosity index (VI) of 125.

Like a lot of mobile hydraulic machines operating in my part of the world, these machines run hot, or hotter than ideal anyway: 80ºC to 90+ºC (176ºF to 194ºF) . And that’s bulk oil temperature, not the hottest part of the system.

After a couple years operating with the OEM’s hydraulic oil, as a cost cutting exercise, the machines were switched to Texaco Rando 46. And this is when the reliability problems started, predominately with varnish/sludge deposits gumming up the electro-hydraulic pilot control valves.

The thing is, Rando 46 has very different chemistry to the OEM branded oil. It has a conventional, zinc-based anti-wear additive package. And while zinc containing oils have been the industry standard for many years, at high temperatures and aided by the presence of water, the zinc compound can combine with other elements in the oil to form sludge.

In other words, with these machines already operating too hot, the oil was unwittingly changed to one with a less stable additive package at high temperatures, resulting in subsequent reliability problems.

Three points:

1. The oil is THE most important component in a hydraulic system. And although it’s always tempting, particularly if the bean counters are allowed to get involved, it’s NOT something that should ever be purchased on price alone.

2. For optimum reliability of the oil and the rest of the machine, keep it COOL, DRY and CLEAN. All three are important. But if you can only manage one, COOL.

3. Switching the type of oil used in a hydraulic machine – without careful and informed consideration, can be a very costly mistake.

And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get “Six Costly Mistakes Most Hydraulics Users Make… And How You Can Avoid Them!” available for FREE download here.