Terry, quick break down of what octane does for you. Higher octanes burn
slower. OK so why do you want a slower burning fuel? Well in cars that are
in poor mechanical condition or are high performance/high compression the
cylinders run hot and frequently ignite the fuel too early. This causes the
explosion of gas against a cylinder that is still traveling up, instead of
pushing it down. This is pinging, and can cause great mechanical problems.
In order to get higher compresion engines (which typically output higher
power) they must slow down the initial combustion to keep the engine from
beating itself up.
Higher octane does not improve performance, it actually does hinder it.
However it is required for many higher performance engines.
That explains the high performance part, as for the poor mechanics, a lot op
people end up using higher octane to treat the sympton and never bother with
the problem (blocked egr valve, sharp edges in combustion chamber, and most
often large carbon deposits on the pistons, valves, and head.)
Rule of thumb, always use the lowest octane that keeps your engine from
pinging.
BTW, while we are on the subject of gas, has anyone seen the GATE gas
station adds that say if your mechanic ever says damage was done by Gate
gasoline they will pay for the repairs. Now is that the biggest crock you
ever heard? What mechanic in their right mind would ever be able to blame
one tank of cause at one station as the cause of damage, and if they did
what lunitic would accept it.
Patrick Bowen
-----Original Message-----
From: Terry L. Thompson [mailto:tlt@digex.net]
Sent: Tuesday, March 28, 2000 3:32 PM
To: spitfires@autox.team.net
Subject: fuel octane
There's a local car show called "Pat Goss's Garage", that appears on a
local station
in Maryland (I'm not sure if it's syndicated or not but he used to or still
does have a
spot on MotorWeek).
Anyhow, this weekend a caller called into his show and asked about Octane.
Pat told
the caller "you should NEVER use gasoline that is higher than the
recommended octane of
fuel for your car. As it may hurt the engine in the long run"
According to Pat, higher octane fuel actually burns slower than lower
octane fuel and
could cause problems with your engine later on. A second caller called in
and mentioned
that she had a follow-up question because in her car, the owners manual
said to use
91 octane fuel and the three choices she had available were 87 89 and 93.
Pat asked the woman, "does it have an R after the 91 in the owner's
manual?" and
she said no...it has an ATI (i think) after the number, and he said that
"They are using a
European scale." and that an R is basically the same thing. And that she
should be using
87 or 89 octane, and never use anything higher.
Finally, a third caller called in and said on his new Mustang, it also
called for 87 octane
but, it would knock and ping so he would fill it every other fill-up with
93 to clean-up
the engine. Pat told HIM that he most likely had an EGR blockage and that
he should have
it looked at as running the 93 octane was not a cure for the problem.
I managed to grab my owner's manual on my way out of the door for work
today and just took
a moment to look at it, and it says to use 91 octane fuel. I'm always using
93 octane (I
figure the engine will burn cleaner and leave fewer deposits), but
evidently I must have it
backwards.
Anyone want to fill in the blanks here?
Terry L. Thompson
'76 Spit 1500
Maryland
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