PROPERTIES OF GASOLINE
For a gasoline
fuel system to function properly, it is necessary that the fuel have the right qualities
to burn evenly no matter what the demands of the engine are. To help you recognize the
qualities required of gasoline used for fuel, lets examine some of the properties of
gasoline and their effects on the operation of the engine.
The ease with which gasoline vaporizes is called volatility. A high volatility
gasoline vaporizes very quickly. A low volatility gasoline vaporizes slowly. A good
gasoline should have the right volatility for the climate in which the gasoline is used.
gasoline is too volatile, it will vaporize in the fuel system. The result will be a
condition called vapor lock. Vapor lock is the formation of vapor in the fuel lines
in a quantity sufficient to prevent the flow of gasoline through the system. Vapor lock
causes the vehicle to stall from lack of fuel. In the summer and in hot climates, fuels
with low volatility lessen the tendency toward vapor lock.
In modern high compression gasoline engines, the air-fuel mixture tends to ignite
spontaneously or to explode instead of burning rather slowly and uniformly. The result is
a knock, a ping, or a detonation. For this reason, gasoline refiners have various ways to
make gasoline that does not detonate easily.
Agasoline that detonates easily is called low octane gasoline. A gasoline that resists
detonation is called high octane gasoline.
rating of a gasoline is a measurement of the ability of the fuel to resist knock or ping.
A high octane rating indicates the fuel will NOT knock or ping easily. It should be used
in a high compression or turbo-charged engine. A low octane gasoline is suitable for a low
give the antiknock value of gasoline. A higher octane number (91) will resist ping better
than a gasoline with a low octane number (83). Each manufacturer recommends an octane
number for their engine.