Organic oils - Wikipedia
Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural metabolic processes. Lipid is the scientific term for the fatty acids, steroids and similar chemicals often found in the oils produced by living things, while oil refers to an overall mixture of chemicals. Organic oils may also contain chemicals other than lipids, including proteins, waxes (class of compounds with oil-like properties that are solid at common temperatures) and alkaloids.
Lipids can be classified by the way that they are made by an organism, their chemical structure and their limited solubility in water compared to oils. They have a high carbon and hydrogen content and are considerably lacking in oxygen compared to other organic compounds and minerals; they tend to be relatively nonpolar molecules, but may include both polar and nonpolar regions as in the case of phospholipids and steroids.
Petrol recent history in United States
From 1998 to 2004, the price of gasoline fluctuated between $1 and $2 USD per U.S. gallon. After 2004, the price increased until the average gas price reached a high of $4.11 per U.S. gallon in mid-2008, but receded to approximately $2.60 per U.S. gallon by September 2009. More recently, the U.S. experienced an upswing in gas prices through 2011, and by 1 March 2012, the national average was $3.74 per gallon.
In the United States, most consumer goods bear pre-tax prices, but gasoline prices are posted with taxes included. Taxes are added by federal, state, and local governments. As of 2009, the federal tax is 18.4? per gallon for gasoline and 24.4? per gallon for diesel (excluding red diesel). Among states, the highest gasoline tax rates, including the federal taxes as of 2005, are New York (62.9?/gal), Hawaii (60.1?/gal), and California (60?/gal). However, many states' taxes are a percentage and thus vary in amount depending on the cost of the gasoline.
About 9% of all gasoline sold in the US in May 2009 was premium grade, according to the Energy Information Administration. Consumer Reports magazine says, "If (your owner?s manual) says to use regular fuel, do so?there?s no advantage to a higher grade." The Associated Press said premium gas?which is a higher octane and costs more per gallon than regular unleaded?should be used only if the manufacturer says it is "required". Cars with turbocharged engines and high compression ratios often specify premium gas because higher octane fuels reduce the incidence of "knock", or fuel pre-detonation. The price of gas varies during the summer and winter months.
For other uses, see Engine (disambiguation).
"Motor" redirects here. For other uses, see Motor (disambiguation).
A V6 internal combustion engine from a Mercedes car
An engine or motor is a machine designed to convert one form of energy into mechanical energy.12 Heat engines, including internal combustion engines and external combustion engines (such as steam engines), burn a fuel to create heat, which then creates a force. Electric motors convert electrical energy into mechanical motion; pneumatic motors use compressed air and others?such as clockwork motors in wind-up toys?use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and eventually motion.