When Should You Change Engine and Hydraulic Oils? A Practical Guide

By Travis Knappett, Kompo® Oil & Grease Specialist at HTS Spares.

Regular oil changes are one of the most critical (and cost-effective!) maintenance tasks for engines and hydraulic systems. Whether you’re running construction equipment, agricultural machinery, industrial plant, or commercial vehicles, using the right oil and changing it at the right time directly affects reliability, efficiency, and operating costs.

At HTS Spares, we supply the KOMPO® range of premium oils and greases, engineered to deliver outstanding protection in demanding operating conditions. In this guide, we explain how often engine and hydraulic oils should be changed, what factors influence oil life, and how oil analysis can safely extend drain intervals.

Why Oil Change Intervals Matter

Oil does far more than just lubricate. In both engines and hydraulic systems, oil:

• Reduces friction and wear
• Carries heat away from critical components
• Suspends contaminants and debris
• Protects against corrosion and oxidation

Over time, oil degrades. Additives are depleted, contamination builds up, and performance drops. If oil is left in service too long, it can lead to increased wear, overheating, component failure, and unplanned downtime - all of which are far more expensive than routine maintenance.

How Often Should Engine Oil Be Changed?

Manufacturer Guidelines Are the Starting Point

Most engine manufacturers specify oil change intervals based on:

• Operating hours (for plant and machinery)
• Mileage (for vehicles)
• Time in service

These guidelines assume normal operating conditions. However, real-world use is often harsher.

Factors That Reduce Engine Oil Life

Engine oil may need to be changed more frequently if equipment is exposed to:

• Heavy loads or towing
• High operating temperatures
• Dusty or dirty environments
• Frequent stop-start operation
• Extended idling

In these conditions, oil degrades faster and accumulates contaminants more quickly.

The Role of High-Quality Engine Oil

Using a premium oil such as KOMPO® engine oils from HTS Spares helps maintain viscosity stability, resist oxidation, and protect against wear - even under heavy use. While high-quality oils can often safely extend service intervals, they still require monitoring to ensure optimal performance.

How Often Should Hydraulic Oil Be Changed?

Hydraulic oil change intervals are less about time and more about oil condition.

Unlike engine oil, hydraulic oil is not exposed to combustion by-products. However, it is extremely sensitive to contamination, which is the leading cause of hydraulic system failure.

Why Contamination Is a Major Risk

Common hydraulic oil contaminants include:

• Solid particles (dust, metal wear debris)
• Water or moisture
• Oxidation by-products

Even microscopic particles can cause:

• Valve sticking
• Pump and seal wear
• Reduced system efficiency
• Overheating

ISO Cleanliness Codes Explained

Hydraulic oil cleanliness is measured using ISO codes, which indicate the number of particles present in the oil. As contamination increases, component life decreases - sometimes dramatically.

Monitoring ISO cleanliness levels allows maintenance teams to:

• Change oil only when necessary
• Prevent premature component failure
• Reduce maintenance costs

The KOMPO® hydraulic oils supplied by HTS Spares are formulated with excellent filtration compatibility and contamination resistance, making them ideal for high-pressure and precision hydraulic systems.

Using Oil Analysis to Optimise Oil Change Intervals

One of the most effective ways to determine when to change oil is through routine oil analysis.

What Does Oil Analysis Measure?

Oil analysis typically checks:

• Viscosity - ensures the oil still maintains proper film strength
• Total Acid Number (TAN) - indicates oxidation and oil degradation
• Particle counts - measures contamination levels
• Water content - identifies moisture ingress

Benefits of Oil Analysis

Regular oil testing helps you:

• Extend oil drain intervals safely
• Detect problems before failures occur
• Reduce unplanned downtime
• Maximise the value of premium oils

When paired with KOMPO® oils and greases, oil analysis allows operators to fully benefit from high-performance lubrication without risking equipment damage.

Grease Matters Too

Oil changes are only part of the picture. Proper greasing is essential for bearings, pins, bushings, and heavily loaded components.

The KOMPO® grease range from HTS Spares offers:

• Excellent load-carrying capability
• Strong adhesion and water resistance
• Protection in high-temperature and high-pressure environments

Using the correct grease at the right intervals significantly reduces wear and extends component life.

Key Takeaways: Best Practice for Oil Changes

• Always start with manufacturer recommendations
• Adjust intervals based on operating conditions
• Monitor hydraulic oil cleanliness using ISO codes
• Use routine oil analysis to make data-driven decisions
• Choose high-quality oils and greases, such as KOMPO® from HTS Spares, for maximum protection

Whether you’re looking to reduce downtime, extend maintenance intervals, or protect high-value equipment, the team at HTS Spares has the lubrication expertise and products to support your operation.

Need advice on the right oil or grease for your equipment?
Please contact me for customised support and tailored lubrication solutions - travis.knappett@htsspares.com / 01432 373350.