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Everything You Always Wanted To Know About Octane
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| July 20, 2002 |
| By: Steve |
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Gas, you say? What's there to know about gas? Actually there's not much
to know about gas, but the little that most people know about gas is wrong.
The misperception about the use of higher octane for more performance is the
most common. I'll discuss the other misconceptions later.
First off- Octane. Race cars and high performance vehicles have higher
compression engines and more advanced ignition timing. This higher
compression can cause premature detonation (relax guys, it happens to
everyone once). To remedy the premature detonation a slower burning fuel is
used. Higher octane numbers mean that the fuel burns slower. The slower
burning fuel can be compressed at a higher ratio without as much fear of
deadly premature detonation, commonly called "pinging." Pinging will
definitely ruin your engine. In modern engines with aluminum pistons this is
an absolute engine killer. With modern replacement engines starting at $2000
+ installation for cheap cars and up to $20,000 for some higher end cars,
it's not something to ignore.
Standard engines are calibrated for regular lower octane fuels. If you put a
slower burning fuel (remember, slower fuel is higher octane), then what
often happens is that all the fuel is not burned. The incomplete detonation
leaves behind carbon deposits that wreak havoc on the valves, piston tops,
EGR and PCV systems. I've often heard people claim that they've used premium
in a car that didn't require it, but now if they try to use regular they get
a pinging detonation problem. That is a self-induced malady. When enough
carbon builds up in the combustion chambers, it effectively raises the
compression by making the chamber smaller. Remember the whole thing about
high compression requiring high octane from the earlier paragraph? If you
have already made this common mistake, there's a way to fix it without
having to admit you screwed up. Take your vehicle immediately to a competent
repair shop and ask for a carbon depletion system. The two I'm familiar with
are the Bilstein and BG engine flush systems. They run a hot detergent
through the engine and remove the carbon buildup. Adding a fuel system
cleaner like BG 44K to the gas tank a couple times a year is a great idea.
The $3 stuff you get at the gas station is merely alcohol- you want a real
cleaner.
Here's what this all means:
If you have a vehicle that is designed for 87 (regular) octane, then use it.
They spent millions of dollars designing the engine, fuel system, sensors
and computers- don't second guess the manufacturer's ability to determine
which gas is best for it. I haven't seen a car yet that is designed for
regular that can adapt to premium. If it could adapt to premium, it probably
would have been designed to be a premium engine from the start.
If you have a vehicle that is designed for 92 (high) octane, then use it.
The engine design was made for it. If you have to, you can often use lower
octanes for short periods of time. The engine has a knock sensor that can
detect "pinging" and will adapt the timing of the ignition system to protect
the engine from damage. The result is lower performance.
So, it's a one way street. You can put regular in a premium vehicle, but you
can't put premium in a regular vehicle. There is a very very rare exception
to this rule. There have been some cars that were designed for premium fuel,
but were then detuned and calibrated for regular low octane. These engines
will adapt to premium and operate just fine. Is the Freelander one of these?
I'm not going to risk my engine to experiment, but I plan to find out from
the Land Rover folks soon - Stay tuned.
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