Automotive Grade LPG, commonly known as Auto LPG, is a refined gaseous automotive fuel composed mainly of propane (C₃H₈) and butane (C₄H₁₀). It is produced during crude oil refining and natural gas processing, then further purified and blended to meet automotive-specific fuel standards.
Auto LPG is used in factory-fitted LPG vehicles and retrofitted petrol engines, offering a cleaner, quieter, and more economical alternative to petrol and diesel while maintaining reliable engine performance.
Chemical Composition & Fuel Quality
Primary Components
Propane and Butane (ratio optimized for vehicle use and climate)
Typical Propane Content: 40–60% (higher in colder regions)
Fuel Quality Controls
Sulfur content extremely low (typically <10 ppm)
Moisture and olefins strictly controlled to protect fuel systems
Ethyl mercaptan added for leak detection
This controlled composition ensures stable vapor pressure, smooth combustion, and long-term injector and engine compatibility.
Key Characteristics of Automotive Grade LPG
High Octane Rating & Knock Resistance
With an octane number of 100–110+, Auto LPG allows higher compression ratios, prevents engine knocking, and delivers smoother acceleration with quieter operation—ideal for urban driving and fleet vehicles.
Low Emissions & Environmental Benefits
Produces 10–15% lower CO₂ emissions than petrol, very low NOₓ, near-zero particulate matter, and virtually sulfur-free exhaust, supporting BS-VI and Euro-VI emission compliance.
Clean Combustion & Engine Protection
Leaves no carbon deposits on valves or pistons, keeps engine oil cleaner, extends oil life, and reduces wear on spark plugs and exhaust systems.
Fuel Economy & Cost Advantage
Although energy density is slightly lower than petrol, the significantly lower fuel cost delivers substantial savings for high-mileage vehicles and commercial fleets.
Safe & Proven Automotive Fuel
Stored in crash-tested, thick-walled cylinders with excess flow valves, pressure relief devices, and automatic shut-off solenoids. LPG disperses upward quickly in open air, reducing fire risk.
Typical Mechanical & Technical Properties
| Property | Typical Value |
|---|---|
| Fuel Type | Propane–Butane blend |
| Research Octane Number (RON) | 100 – 110+ |
| Auto-Ignition Temperature | ~470 – 500°C |
| Calorific Value | 46 – 50 MJ/kg |
| Liquid Density | 0.50 – 0.58 kg/L |
| Vapor Pressure @ 20°C | 2 – 8 bar |
| Flammability Range | 2% – 10% in air |
| Sulfur Content | <10 ppm |
| Storage State | Liquefied under pressure |
| Appearance | Colorless, odorized |
Refining & Production Process
Crude Oil Refining
LPG recovered during atmospheric distillation and catalytic cracking processes
Natural Gas Processing
Extracted from Natural Gas Liquids (NGLs)
Purification
Removal of sulfur compounds, moisture, and acidic gases
Blending & Quality Control
Propane–butane ratio optimized for vehicle engines and tested for volatility, vapor pressure, sulfur content, and composition
Odorization
Safety odorant added before distribution
Vehicle Compatibility
Factory-Fitted LPG Vehicles
Cars, three-wheelers, and dual-fuel petrol + LPG vehicles designed for Auto LPG
Retrofitted Vehicles
Petrol vehicles fitted with certified LPG conversion kits, including modern sequential injection systems
Not Suitable For
Diesel engines (without specialized conversion)
Non-approved or uncertified retrofits
Storage & Distribution
Vehicle LPG Cylinders
Toroidal (spare-wheel type) and cylindrical tanks made from high-strength steel and tested for pressure, fire, and crash resistance
Auto LPG Fuel Stations
Dedicated LPG dispensing pumps with metered, temperature-compensated fueling and safety-interlocked nozzles
Applications of Automotive Grade LPG
Passenger Vehicles
Cars, taxis, and ride-sharing fleets
Light Commercial & Public Transport
Auto-rickshaws, delivery vans, city transport vehicles
Fleet & Institutional Use
Corporate fleets, government vehicles, logistics and service vehicles
Comparison with Petrol & Diesel
| Parameter | Auto LPG | Petrol | Diesel |
|---|---|---|---|
| Octane | High (100+) | Moderate | NA |
| Emissions | Low | High | Very High |
| Engine Noise | Low | Medium | High |
| Maintenance | Low | Medium | High |
| Fuel Cost | Low | High | Medium |
Safety & Regulatory Compliance
Complies with IS, EN, and ASTM automotive LPG standards, BS-VI and Euro-VI emission norms, and certified LPG conversion and inspection requirements.
Regular inspection, leak testing, and adherence to approved installation practices ensure safe and reliable long-term operation.
Automotive Grade LPG is a clean, high-octane, and economical automotive fuel that delivers lower emissions, smoother engine performance, and reduced operating costs—making it an ideal solution for urban mobility, commercial fleets, and environmentally conscious vehicle owners.