Specific Gravity:Specific gravity measures the density of gasoline compared to water. A specific gravity of 0.72 means that the gasoline weighs 0.72 times as much as water, or it is 72 percent of the weight of water. Most gasolines weigh about 6.2 lbs per gallon.
Volatility:Volatility refers to the ease with which a gasoline turns from a liquid to a vapor. Low volatility refers to low RVP, indicating fewer light hydrocarbons in the gasoline's front end. Southern California summer-grade gasolines have low volatility. Winter-grade gasolines in Michigan have high volatility, or high RVP, to start the engine easier in sub-zero temperatures.
Ethers:MTBE, TAME, and ETBE are the most common ethers available for gasoline use. They have higher-octane values than typical gasoline. Like the alcohols, they will increase the octane quality of street gasoline. Ethers do not have an affinity for water, will not separate from gasoline, and blend like a hydrocarbon. When ethers are used as additives, the enthusiast still does not know what his final octane number is. Chemicals such as MTBE are currently illegal in 12 states, including California.
TEL (Lead):Lead, Tetraethyl Lead, or TEL is a very effective octane improver used in many racing and aviation gasolines. It is extremely toxic in its pure form and has been illegal in any street-driven vehicle in the U. S. since January 1996. It will poison oxygen sensors and catalytic converters. It is sold in a much-diluted form by at least one vendor-but not in California because of restrictions on metallic additives. Again, one still does not know the octane number of the final blend.
OLE- Olephine. These are the bad actors that are generally kept at a low level because they cause deposits. They are hard and costly to remove from the fuel. In California, OLE (carb phase 3 gasoline) has to be less than 10 percent. California has stricter requirements because of emission and air pollution problems; the EPA sets their own specifications.