Bismarck,
I am not an expert in this, but i will try my best to relate what
my car mechanic told me about the different octane and why
different cars need different octanes.
First you will come across the term "anti-knocking index" in your
instruction manuals. Anti-knocking index (or AKI) is the european
term for Octane.
WHy it is called AKI is because it is the index (or octane) your
car requires to prevent yoru engine from "Knocking".
Before I continue, I think what my car mechanic told me applies
only to fuel-injection engines. So Rolls-Royce and RX-7 owners....
dun rely on my information. hehehe. And if you are a Rolls-Royce
owner, dun think paying for V-power matters to you thus dun jam up
those stations offering 8% discounts.
A higher octane fuel is suppose to combust (explode) more than
lower ones. When fuel is injected into the cylinder, the piston
would be at the down position and when the spark ignites and
explodes the fuel, it pushes the piston up to the cylinder, rotate
the cams and axle.
So in a 4 cylinder engine, pistons 1 and 3 will be down and 2/4
will be up (and vice versa). The rotation of your wheels is the
result of this cycle of pistons going up and down.
Thus using a lower octane fuel will not combust as much and wun
push the piston as high it is supposed to and those the rotation
would be as complete. This uncompleted rotation four-stroke cycle
of the engine thus will cause damage. Not sure of the details, i
got a sketchy picture of it, but choose not to relate to you all
incase it confuses you further.
Anyway, the mechanic also say you may use a lower octane fuel if
you are driving highway because the increased consistency in
revving will make up for the lost rotation and would bring the
machine operation into the threshold of the engine design. This
however haven't been proven by him yet. And this mechanic is in
North America, so his definition of "highway driving" is about 2-4
hours stretches at 130-160km/h. Not like our 20mins stretches of
90km/h at PIE.
INterestingly, I would like to point out the cars are also "timed"
and localised to the market it would be should. Since most Asian
countries will tax cars according to engine size, we tend to buy
smaller engine sizes but demand more power from that same engine.
THe same is true for Europe and that explains why alot of models
will have Supercharged or Turbocharged engines (e.g. Benz
Kompressors and Volvos). Japanese cars respond by incorporating
Variable timing (VTEC, VVTi, VVTC).
Consequently, manufacturers will "time up" or "time down" the
engine according to the market. For example, a Nissan X-trail in
Singapore (timed up) uses the QR25DE engine and require a 95
Octane. But in North America, the Nissan Sentra V-Spec or Altima
uses the same QR25DE (timed down) but needs only 89 Octane. The
difference, X-trial has an output of 179 horsepower and the latter
175 hp.
It is possible for you to "time down" your car in Singapore to
require a lower octane level. It takes about 15-20mins but you will
have a decreased output by about 2-6 horsepowers.
