Show What You Should Know About Octane Ratings Miles per gallon of gasoline is an important priority but there's another money-saving you should the least expensive gasoline for your make and model YOU SHOULD buy the lowest octane fuel your engine will bum without The knocking phenomenon-detected as a sharp metallic noise-occurs when the air-fuel mixture burns unevenly inside your car's In addition to causing a lots in power and fuel knocking also can damage expensive engine requirements can vary between individual cars and An engine that is out of for requires a higher octane than one that is property Driving such as stop and go increases combustion deposit build-up and the octane Many other factors also can influence the octane requirements of your The higher the air or engine the higher oc-taine fuel your car The lower the altitude and the relative the higher the octane UNDERSTANDING octane ratings can be confusing because different methods of the ratings can produce different Your owner's manual recommends the minimum octane rating of fuel for your particular THE OCTANE number is listed as Research Most late model cars are designed to operate on regular grade usually specified as 91 octane You may that the owner's manual octane rating for regular gasoline is three or four numbers higher than the regular grade octane rating posted on service station This is because the octane rating that the Cost of Living Council requires be posted on the pumps is determined differently than the Research The octane rating of gasoline is determined in the laboratory using a specially designed When the gasoline is tested for engine knocking under mild operating conditions of low engine speed and low fuel-air mixture the resulting figure is called Research A TEST run under more severe conditions of higher engine speeds and higher fuel-air mixture tempera tures causes the same gasoline to knock sooner and yields a relatively low octane This is called Motor Averaging the gasoline's Research and Motor octane ratings yields the octane number that is posted on the gasoline don't worry if the octane rating of the gasoline that you buy is a little lower than that recommended for your your engine starts to In that just switch to a slightly higher octane fuel until the knocking |