Complete Guide to AMSOIL Hydraulic Oil for Bobcat Skid Steers

Selecting the right hydraulic oil is one of the most important maintenance decisions for your Bobcat skid steer. While Bobcat manufactures its own branded fluids, many operators choose AMSOIL synthetic hydraulic oils for superior performance, extended drain intervals, and all-season capability. Here's everything you need to know.

Understanding Viscosity: The Foundation of Selection

Viscosity—the thickness of the oil—is the single most critical factor in hydraulic fluid selection. Using an incorrect weight can result in sluggish operation, cavitation damage, inadequate lubrication, or system noise.

AMSOIL 5W-30 100% Synthetic Tractor Hydraulic/Transmission Oil is widely regarded as the gold standard for year-round use in Bobcat machines. This multi-grade fluid flows reliably from below -58°F in harsh winter conditions while maintaining protective film thickness in summer heat. For many operators, this eliminates the need for seasonal oil changes entirely. With its excellent all-weather performance and lower cost point, it's an excellent choice for operators in variable climates.

AMSOIL ISO 46 100% Synthetic Multi-Viscosity Hydraulic Oil serves machines operating in moderate to warm climates. ISO 46 is the industry standard for many newer mobile hydraulic systems and is often explicitly recommended for modern Bobcat loaders that specify an AW-46 grade. This mid-range viscosity balances protective thickness with efficient cold-weather flow.

AMSOIL ISO 32 Hydraulic Oil is optimized for operations in extreme cold climates where a thinner fluid ensures immediate, uninhibited flow and minimal warm-up time. While less common for general-purpose use, it's ideal if your Bobcat operates primarily in frigid conditions.

AMSOIL ISO 68 Commercial-Grade Hydraulic Oil is reserved for very warm or hot-climate applications where higher viscosity is required for specific system demands.

The Varnish-Control Advantage

One of AMSOIL's defining features is its advanced varnish-control technology, particularly important in modern Bobcat systems that operate under extreme pressures and temperatures.

How Varnish Forms and Why It Matters

Varnish is a soft, sticky deposit of oil degradation byproducts that accumulates on metal surfaces inside your hydraulic system. Over time, it hardens into a protective film that restricts flow, sticks valves, clogs servo ports, and creates the dreaded "spongy" or sluggish hydraulic response that many operators experience with conventional oils.

AMSOIL's Two-Part Solution

AMSOIL combats varnish through superior synthetic base oils and specialized anti-varnish additives. The synthetic base stocks naturally resist thermal and oxidative breakdown—the root cause of varnish formation in conventional petroleum oils. Additionally, AMSOIL fortifies its Multi-Viscosity Hydraulic Oils with chemical additives that react with varnish "building blocks" as they form, preventing them from bonding to metal surfaces in the first place.

Practical Benefits for Your Bobcat

This translates into measurable advantages: pumps, motors, valves, and servo mechanisms stay cleaner and more responsive, reducing jerky operation and improving precision when moving attachments or making fine adjustments. Many operators report that hydraulic response feels tighter and more immediate after switching to AMSOIL. Additionally, cleaner systems require less frequent filter replacements and maintenance interventions, extending equipment uptime and reducing overall ownership costs.

Performance Advantages You'll Notice

Reduced Noise: One of the most commonly reported benefits is a dramatic reduction in the high-pitched "hydrostatic whine" that characterizes many Bobcat loaders under load. This noise reduction often becomes apparent within the first operating hours after an oil change.

Superior Heat Dissipation: Synthetic base oils naturally resist thermal breakdown better than conventional mineral oils, helping your hydraulic system run cooler even under sustained heavy-load operation. This is especially valuable during hot-weather months or intensive work cycles.

Rapid Water Separation: AMSOIL allows water contamination to separate quickly so it can be drained during maintenance, rather than emulsifying (turning milky) like some competitive fluids. This prevents pump cavitation and corrosion damage.

Seal Conditioning: AMSOIL contains conditioners that keep hydraulic hoses, seals, and gaskets flexible and supple, reducing the risk of leaks, blown seals, and expensive hose failures.

Critical: Always Verify Your Manual

While AMSOIL fluids are "Warranty Secure" and meet major industry specifications (Parker Hannifin HF-0, John Deere J20C, and others), your specific Bobcat model's requirements must take precedence. Different model years and designs call for different fluids.

Older Bobcat models (particularly older 753, 763, and earlier skid steers) may require conventional engine oil equivalents like 10W-30 or 15W-40 for their hydraulic systems.

Newer Bobcat models often specify Bobcat's proprietary cool-climate or warm-climate hydrostatic fluid blends, which have unique additives and performance characteristics designed for advanced closed-center hydraulic circuits.

Before refilling, consult your Bobcat Operation & Maintenance Manual to confirm the exact viscosity and specification your machine requires. Using the wrong fluid, even if it seems similar, can void your warranty and cause performance issues.

Product Selection and Capacity Guide

Here's a quick reference for common Bobcat models and their approximate hydraulic system capacities:

Bobcat S570 Skid-Steer: Approximately 9.5 gallons total system capacity. Recommended: AMSOIL 5W-30 Synthetic Tractor Oil (Product codes: ATH05-EA for 5-gallon pail, ATH01-EA for 1-gallon)

Bobcat S650 Skid-Steer: Approximately 11.9 gallons total system capacity. Recommended: AMSOIL ISO 46 Multi-Viscosity (Product codes: HVI05-EA for 5-gallon pail, HVI01-EA for 1-gallon)

Bobcat T590 Compact Track Loader: Approximately 9.5 gallons total system capacity. Recommended: AMSOIL 5W-30 Synthetic Tractor Oil (ATH05-EA or ATH01-EA)

Older Models (e.g., 753, 763): Approximately 8 quarts total system capacity. Recommended: AMSOIL ISO 46 Multi-Viscosity (HVI05-EA or HVI01-EA)

Important note: The capacities listed above represent the total system capacity, which is what you need for a complete fluid change. The actual reservoir is smaller (typically 2-3 gallons for S-series models), so don't be surprised when you pour in less fluid than expected—the remainder is distributed throughout lines, cylinders, and the transmission/torque converter.

Final Recommendation

For most Bobcat operators seeking a single, all-season solution that delivers quieter operation, superior wear protection, and extended maintenance intervals, AMSOIL 5W-30 Synthetic Tractor Hydraulic Oil is the logical choice. For newer machines that specifically call for ISO 46, AMSOIL's ISO 46 Multi-Viscosity hydraulic oil provides the same varnish-control benefits in the correct viscosity grade.

Always start by confirming your manual's requirements—it's the single most important step. From there, AMSOIL's synthetic formulations provide the performance enhancement and reliability that justify the modest premium over conventional fluids.