In this article, I’ll walk you through the best types of used oils for solvent extraction, what makes them suitable, and what to avoid.
Why Solvent Extraction?
Solvent extraction is ideal for removing:
- Aromatics
- Asphaltenes
- Oxidation byproducts
- Additives and metal impurities
The goal is to isolate and recover Group I or Group II base oils that can be reused or sold, rather than burned or discarded.
Best Types of Used Oils for Solvent Extraction
Here are the most compatible waste oils based on actual plant performance:
- Used Engine Oil
- Source: Vehicles, diesel engines, generator
- Contains carbon, metal particles, and additives
- Very common and widely available
- Works well after pre-treatment (filtration + dehydration)
- Yield: 60–75% base oil recovery (varies by technology and condition)
- Used Hydraulic Oil
- Source: Construction, manufacturing, heavy machinery
- Low additive content
- Highly stable base stock, ideal for extraction
- Fewer contaminants = higher base oil yield
- Yield: Up to 80% high-grade base oil
- Used Gear Oil / Transmission Oil
- High-viscosity, additive-rich
- Contains sulfur, phosphorus, and EP agents
- Still usable after solvent pre-cleaning
- May require desulfurization or blending
- Used Transformer Oil (Mineral Oil Type)
- Stable, light fraction oil
- Usually low in sludge
- Great for extracting high VI base oils
- Needs PCB testing before use (for old batches)
- Blended Industrial Lubricants
- Mixed origin, including synthetic blends
- Feedstock must be tested and classified
- Acceptable if mineral base oil dominates
Used Oils to Avoid (or Use with Caution)
| Used Oil Type | Base Oil Yield | End Product Notes |
| Used Engine Oil | 60–75% | Slightly darker base oil |
| Hydraulic Oil | 70–80% | Light color, high VI |
| Gear Oil | 55–65% | Higher sulfur, thicker |
| Transformer Oil | 75–85% | Light, clean output |
| Mixed Lubricants | 50–70% | Variable results |
Key Properties That Determine Suitability
Base Stock Type:
– Mineral oils = ideal
– Synthetics = variable
Additive Load:
– Lower additive oils are easier to extract
– Dispersants and detergents increase difficulty
Sludge Content:
– More sludge = more solvent usage and waste
Water and Emulsion:
– Must be removed before extraction to prevent yield loss
Heavy Metal Content:
– Increases the need for chemical pre-treatment
Pre-Treatment Required Before Solvent Extraction
To make used oil suitable for solvent extraction, basic pre-treatment steps include:
- Gravity settling or centrifugation
- Filtration(down to 5–10 microns)
- Water separation
- Optional: vacuum dehydration
This preparation increases yield, extends solvent life, and improves end-product purity.
Solvent Extraction Yield by Oil Type (Typical Range)
| Used Oil Type | Base Oil Yield | End Product Notes |
| Used Engine Oil | 60–75% | Slightly darker base oil |
| Hydraulic Oil | 70–80% | Light color, high VI |
| Gear Oil | 55–65% | Higher sulfur, thicker |
| Transformer Oil | 75–85% | Light, clean output |
| Mixed Lubricants | 50–70% | Variable results |
Why It Matters
Choosing the right feedstock means:
- Less solvent usage
- Higher base oil recovery
- Lower waste output
- Faster ROI for your plant
Whether you're running a small batch unit or a continuous solvent extraction plant, feedstock matters more than almost anything else.
Start Recovering High-Quality Base Oil Today
We design and build solvent extraction plants that handle a wide variety of waste oil types. Our systems are built for:
- High base oil yield
- Flexible feedstock input
- Solvent recovery and reuse
- Environmental compliance