LPG (Propane) Conversion for Cars: Costs, Benefits, and Fuel Economy

What Is LPG Conversion?

Liquefied petroleum gas (LPG, or propane) vehicle conversions add a secondary fuel system to an existing gasoline engine. The vehicle can run on either LPG or gasoline — switching automatically or manually between the two. LPG burns cleanly, costs significantly less than gasoline in most markets, and produces lower CO₂ per kilometer driven.

How LPG Systems Work

LPG is stored in a liquid state in a purpose-built tank (usually in the trunk or under the vehicle). A vaporizer/regulator converts liquid LPG to gas before it enters the engine intake. Sequential injection systems inject LPG into each port individually (like gasoline) for maximum efficiency and emissions compliance.

Fuel Economy vs Gasoline

LPG has about 75% of the energy density of gasoline per liter, so you'll use approximately 20–25% more LPG volume than gasoline for the same distance. However, since LPG costs 30–60% less per liter/gallon than gasoline in most markets, the per-mile cost is typically 25–40% lower.

Conversion Cost

A professional LPG conversion costs $1,500–$3,500 depending on system type and vehicle. Payback period at typical US LPG/gasoline price differentials: 2–4 years for high-mileage drivers. In markets with larger price gaps (UK, Turkey, Poland), payback can be under 2 years.

Emissions Impact

LPG produces approximately 15–20% less CO₂ per mile than gasoline, and significantly less NOx and particulate matter. Catalytic converter compatibility varies by system quality — sequential injection systems maintain full emissions compliance.