Can Used Engine Oil or Hydraulic Oil Be Recycled Into Diesel?
A Practical Guide to Converting Waste Oils into Clean Fuel
As someone working daily in oil recycling technologies, I get this question often:
“Can I recycle used engine oil or hydraulic oil into usable diesel fuel?”
The short answer is yes — and it’s not just possible, it’s profitable, efficient, and increasingly necessary. Below, I explain exactly how it works, what’s required, what output you can expect, and what kind of diesel quality results from this process.
What Makes Used Engine Oil and Hydraulic Oil Suitable for Diesel Recovery?
Both engine oil and hydraulic oil are hydrocarbon-based lubricants. That means they contain long-chain molecules similar to those found in diesel fuel. Even after usage, these molecules remain, though contaminated by:
- Carbon particles (soot)
- Water and coolant residues
- Heavy metals
- Oxidation byproducts
- Additive breakdown compounds
Despite the impurities, their base structure still holds fuel value. Using the right technology, we can recover that value effectively.
How Is It Done? The Conversion Process in 4 Stages
We use a thermal and chemical distillation process that converts these oils into diesel:
Pre-Treatment & Dehydration
We remove water, solids, and antifreeze. This step increases diesel yield and prevents foaming or cracking.
Vacuum Distillation
The core process: heating oil in the absence of oxygen. Light and middle distillates evaporate and condense into clean liquid hydrocarbons.
Catalytic Upgrading
We refine the raw distillate using catalysts. This improves color, reduces sulfur, and increases cetane number.
Polishing & Filtration
Final filtration removes residual ash and fine impurities. The result is ready-to-use diesel fuel.
Diesel Yield from Engine Oil vs. Hydraulic Oil
| Waste Oil Type | Diesel Yield (L/ton) | Quality Notes |
| Used Engine Oil | 750–800 | Moderate sulfur, dark color |
| Hydraulic Oil | 800–850 | Low ash, cleaner, lighter diesel |
Hydraulic oil typically gives a higher yield due to fewer impurities and additives.
Engine oil requires more refining but still produces fuel-grade diesel suitable for off-road, generator, or industrial use.
Diesel Quality: Can It Be Used in Vehicles?
Yes, with proper refining:
- Color: Water-white to light yellow
- Sulfur: <0.05% (with desulfurization unit)
- Cetane Index: 45–50
- Pour Point: -5°C to -15°C
- Ash content: <0.01%
With additional treatment, it can meet EN590 or ASTM D975 standards, depending on end use.
Common applications include:
- Diesel generators
- Agricultural machinery
- Industrial burners
- Local fleet vehicles (non-Euro 6 markets)
Why Recycle These Oils Into Diesel?
The alternative — incineration or dumping — pollutes and wastes valuable hydrocarbons. Recycling into diesel:
- Reduces dependence on crude oil
- Cuts waste management costs
- Generates a marketable fuel product
- Supports circular economy goals
- Lowers CO₂ footprint for industries
Common Misconceptions (and the Truth)
| Misconception | Reality |
| Used oil can’t be reused | The diesel produced is of low quality |
| The diesel produced is low quality | With the right setup, it matches or exceeds basic specs |
| ROI is usually under 12–18 months for most operators | Modern systems are clean, sealed, and compliant |
| Recycling is not profitable | ROI usually under 12–18 months for most operators |
Ready to Start Turning Waste Oils into Diesel?
We build complete waste oil to diesel systems from 5 TPD to 100 TPD. Our technology:
- Handles mixed oils (engine, hydraulic, transmission)
- Achieves high recovery rates (up to 85%)
- Produces clean, stable diesel fuel
- Includes setup, training, and ongoing support
Let’s talk about your waste oil type and project goals.
