Substituting AW 32 Hydraulic Oil for TO-4 in a CAT 320C

[MikePhua]

When a hydraulic hose bursts on a CAT 320C excavator, operators may wonder if they can safely substitute AW 32 (10-weight) hydraulic oil for Caterpillar’s recommended TO-4 10-weight oil to get back to work quickly. Understanding the differences and risks helps make an informed decision.
Key Differences Between AW 32 and TO-4
AW 32 is a standard anti-wear hydraulic oil designed for general hydraulic systems. TO-4, however, is a Caterpillar-specific fluid formulated for both transmission and hydraulic systems, with additives for wear protection, friction control, and seal compatibility.
Possible Short-Term Substitution
Operators discuss that in an emergency, AW 32 can be used temporarily to top off or refill the hydraulic system to prevent damage from running dry. However, this should only be a short-term solution until the correct TO-4 oil is available.
Risks of Using AW 32 Long-Term
Using AW 32 long-term may affect pump wear, clutch performance, and seals because it lacks the specific friction modifiers and additive package that TO-4 provides. This could lead to increased component wear, slipping clutches (where applicable), or seal degradation.
Practical Recommendations
If substitution is unavoidable, drain and flush the system as soon as possible and refill with the correct TO-4 fluid. Keeping a small supply of TO-4 on hand can prevent downtime and ensure the machine stays within manufacturer specifications.
Operator Experiences
Some operators have used AW 32 in emergencies without immediate issues but agree it’s not a permanent fix. They emphasize that the cost of using the wrong oil long-term can outweigh the savings in downtime.
Conclusion
AW 32 hydraulic oil can be used temporarily in a CAT 320C if a hose bursts and TO-4 oil is not immediately available, but it’s essential to return to the recommended fluid as soon as possible. Following proper fluid guidelines protects the machine’s hydraulic system and extends its lifespan.