CNG carrier ships, especially when the infrastructure for pipelines or LNG is not in place. At short distances, undersea pipelines are often more cost-effective, and for longer distances, LNG is often more cost-effective. Advantages Natural gas vehicles have lower maintenance costs than other hydrocarbon-fuel-powered vehicles. CNG fuel systems are sealed, preventing fuel losses from spills or evaporation. Increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil. Being a gaseous fuel, CNG mixes easily and evenly in air. CNG is less likely to ignite on hot surfaces, since it has a high auto-ignition temperature (540 °C), and a narrow range (5–15 percent) of flammability. CNG-powered vehicles are considered to be safer than petrol-powered vehicles. Less pollution and more efficiency: CNG emits significantly less pollution directly than petrol or oil when combusted (e.g., unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen oxides (NOX), sulfur oxides (SOx) and PM (particulate matter)). For example, an engine running on petrol for 100 km produces 22 kilograms of , while covering the same distance on CNG emits only 16.3 kilograms of . The lifecycle greenhouse gas emissions for CNG compressed from California's pipeline natural gas is given a value of 67.70 grams of -equivalent per megajoule (gCO2e/MJ) by CARB (the California Air Resources Board), approximately 28 percent lower than the average petrol fuel in that market (95.86 gCO2e/MJ). CNG produced from landfill biogas was found by CARB to have the lowest greenhouse gas emissions of any fuel analyzed, with a value of 11.26 gCO2e/MJ (more than 88 percent lower than conventional petrol) in the low-carbon fuel standard that went into effect on January 12, 2010. Due to lower carbon dioxide emissions, switching to CNG can help mitigate greenhouse gas emissions. However, natural gas leaks (both in the direct use and in the production and delivery of the fuel) represent an increase in greenhouse gas emissions. The ability of CNG to reduce greenhouse gas emissions over the entire fuel lifecycle will depend on the source of the natural gas and the fuel it is replacing. Drawbacks Compressed natural gas vehicles require a greater amount of space for fuel storage than conventional petrol-powered vehicles. Since it is a compressed gas, rather than a liquid like petrol, CNG takes up more space for each GGE (petrol gallon equivalent). However, the cylinders used to store the CNG take up space in the trunk of a