Dầu gốc, dầu tổng hợp, dầu bán tổng hợp, dầu khoáng, mineral oi, synthetic oil, semi synthetic oil

Base Oil: What You Need to Know

I. What is Base Oil?
Base oil is the foundational component in lubricants, accounting for 70–99% of the formulation. It serves as the primary raw material in engine oils, hydraulic oils, compressor oils, gear oils, greases, and other industrial fluids.
However, base oil alone lacks ideal lubricating properties and only becomes effective when blended with additives to form finished lubricants that meet stringent technical requirements.

II. API 1509 Base Oil Classification
The American Petroleum Institute (API) classifies base oils into five groups based on:
• Sulfur content (S)
• Percentage of unsaturated hydrocarbons
• Viscosity Index (VI)

Group	Type	Sulfur Content		% Unsaturated Hydrocarbons	VI (Viscosity Index)		Origin
I	Solvent-refined mineral oil	> 0.03%		> 10%	80–120		Petroleum
II	Hydrocracked mineral oil	≤ 0.03%		≤ 10%	80–120		Petroleum
III	Severely hydrotreated oil	≤ 0.03%		≤ 10%	> 120		Petroleum (near-synthetic)
IV	Polyalphaolefin (PAO)	Very low		None	> 125		Synthetic
V	Esters, PAG, Silicone, etc.	Varies	Varies		Varies	Synthetic / Natural

III. Common Types of Base Oil

3.1. Mineral Base Oil (Groups I, II, III)
• Derived from crude oil using solvent refining, dewaxing, hydrocracking.
• Advantages: Low cost, easy to produce, suitable for standard applications.
• Disadvantages: Lower thermal and oxidative stability, more deposits.
Popular types: SN150, N150.

3.2. Synthetic Base Oil (Groups IV, V)
• PAO (Group IV): Produced from olefin polymerization → highly stable, high VI.
• Ester/PAG (Group V): Highly polar, excellent performance in harsh environments.
Advantages:
• Excellent oxidative & thermal stability
• Good low-temperature fluidity
• Low volatility, minimal deposits
Applications: Premium engines, compressors, aviation, food-grade uses.

3.3. Semi-Synthetic Oil
• Blend of Group II/III mineral oil with some synthetic base oil (PAO/Ester).
• Advantages: Better performance than mineral oil, more affordable than full synthetics.
• Applications: Motorcycle engine oils, light to medium-duty industrial use.

IV. Composition & Chemical Structure

4.1. Mineral Base Oils (Groups I–III)

• Paraffinic: RCH₂–CH₂–CH₃ → stable, high VI
• Naphthenic: Cyclohexane → lower VI
• Aromatic: Benzene ring, unstable, often removed

4.2. Synthetic Base Oils (Groups IV–V)
• PAO: (–CH₂–CH(CH₃)–)ₙ → highly stable, low deposit formation
• Ester: Contains COO– group, polar, self-cleaning, heat-resistant
• PAG: Highly polar, poor compatibility, used separately

V. Key Technical Properties of Base Oil

Property	Function
Viscosity	Lubrication and surface protection
Viscosity Index (VI)	Maintains viscosity with temperature change
Low Volatility	Reduces oil loss at high temperatures
Oxidation Stability	Prevents degradation over time
Heat & Deposit Control	Protects system, extends equipment life
Additive Compatibility	Ensures stable blending and performance

VI. Base Oil Production Flowchart

6.1. Mineral Base Oil:
A [Crude Oil] → B [Light Fraction Separation]
→ C [Solvent Refining / Hydrocracking]
→ D [Desulfurization & Dewaxing]
→ E [Hydrofinishing / Isomerization]
→ F [Base Oil Group I/II/III]

6.2. Synthetic Base Oil:
G [Pure Hydrocarbons] → H [Polymerization / Esterification]
→ I [PAO / Synthetic Ester Base Oil]

VII. Applications by Base Oil Group

Group	Typical Applications
I	Industrial lubricants, older engines
II	General engine oils, hydraulic fluids
III	Truck oils, high-performance engines
IV	Aviation, extreme environments
V	Refrigeration, food industry, specialty fluids

VIII. Technical Comparison Table

Property	G.I	G.II	G.III	G.IV (PAO)	G.V (Ester/PAG)
Cost	Low	Mid	Mid–High	High	Very High
Oxidation Stability	Avg	Good	Very Good	Excellent	Varies
Low Temp	Poor	Avg	Good	Very Good	Very Good
High Temp	Avg	Good	Very Good	Very Good	Very Good
Compatibility	Good	Good	Good	Good	Limited
VI (Index)	80–120	90–120	>120	>125	100–180

IX. Typical Viscosity Values

Base Oil Type	Viscosity @40°C (cSt)	Viscosity @100°C (cSt)	VI
Group I SN150	32–36	~5.4	~95
Group II N150	32–34	~5.5	~110
Group III 4cSt	~40	~7.0	125–135
Group IV PAO 4	~40	~7.1	>140

X. Practical Use & Recommendations

Application	Recommended Base Oil	Reason
High-performance engines	Group III / IV / V	Thermal stability, anti-wear
Air compressors	Group II / IV	Low volatility, stable
Cold hydraulic systems	Group III / IV / V	Good fluidity
Food/Pharma processing	Group V (Safe Esters)	Meets NSF / FDA standards

XI. Base Oil Compatibility

Combination	Compatibility	Notes
Group I ↔ II	OK	Common blend
Group II ↔ III	OK	Easy to mix
Group III ↔ PAO	OK	Used in semi-synthetics
PAO ↔ Ester	OK, conditional	Ester enhances polarity
Ester ↔ PAG	NOT OK	Incompatible
PAG ↔ Groups I–IV	NOT OK	Phase separation, use separately