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Discussion Starter · #1 ·
Hello everybody,

I want to raise a question here: what are your thoughts about octane gas?
I used the 87 gas for my car until I realized (after a while, to be honest) that my car needs at least 91. Since almost a year I've been using 91 and the engine runs well, I can feel more power and I'm happy with.
I've done a couple of tests and it turned out that with 87 I can drive more kilometers than with 91, but (weird) with 91 there is a lower fuel consumption... With 87 I had 9.4l/100km and with 91 I had 8.7l/100km. I realized that for a difference of 10 cents per litter I can have a better driving.
But, nowadays, with all the price increases, it "hurts" my wallet everytime I fill up the tank at a higher price than anyone else. Weird thing, my friend is driving a Nissan Altima 2008 and he is using 87. Newer engine, low quality of gas? How come?
So, what do you use for driving your VW's, guys?
Mark
Passat '99, 1.8T
 

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Discussion Starter · #2 ·
Re: Octane gas (mgm)

CAN HIGHER OCTANE FUELS GIVE ME MORE POWER?
On modern engines with sophisticated engine management systems, the engine can operate efficiently on fuels of a wider range of octane rating, but there remains an optimum octane for the engine under specific driving conditions. Older cars without such systems are more restricted in their choice of fuel, as the engine can not automatically adjust to accommodate lower octane fuel. Because knock is so destructive, owners of older cars must use fuel that will not knock under the most demanding conditions they encounter, and must continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away. If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy. You may be able to change octanes between seasons ( reduce octane in winter ) to obtain the most cost-effective fuel without loss of driveability.
Once you have identified the fuel that keeps the engine at optimum settings, there is no advantage in moving to an even higher octane fuel. The manufacturer's recommendation is conservative, so you may be able to carefully reduce the fuel octane. The penalty for getting it badly wrong, and not realising that you have, could be expensive engine damage.

DOES LOW OCTANE FUEL INCREASE ENGINE WEAR?
Not if you are meeting the octane requirement of the engine. If you are not meeting the octane requirement, the engine will rapidly suffer major damage due to knock. You must not use fuels that produce sustained audible knock, as engine damage will occur. If the octane is just sufficient, the engine management system will move settings to a less optimal position, and the only major penalty will be increased costs due to poor fuel economy. Whenever possible, engines should be operated at the optimum position for long-term reliability. Engine wear is mainly related to design, manufacturing, maintenance and lubrication factors. Once the octane and run-on requirements of the engine are satisfied, increased octane will have no beneficial effect on the engine. Run-on is the tendency of an engine to continue running after the ignition has been switched off, and is discussed in more detail in Section 8.2. The quality of gasoline, and the additive package used, would be more likely to affect the rate of engine wear, rather than the octane rating.
 

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Re: Octane gas (mgm)

turbo/supercharger = no less then 91.. im sure you can use 89, but it might start pinging and be a lot more slugish
naturally aspirated motor = whatever you want.. 87 or 89 or 91.. just because its a newer motor dosent mean it needs higher octane gas..
i know some people on this forum swear by 94 because their chips are tuned for them and etc, i personally use 94 also because thats the best gas for my car.
 

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Re: Octane gas (followthereaper89)

you have a 1.8t, the knock detection is very intelligent, it can pin point knock down to each cylinder.
what im trying to say, you can run 87 octane just dont expect any performance as the ecu will retard timing to prevent the knock condition from happening.

moral of the story run 91octane.
 

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I like higher post counts?
I use 94 because my car is chipped for it.
Sometimes when 94 isn't around I'll put in 10 bucks of 91 to hold me over and you can really tell the difference... Or maybe it's because my turbo is blown.. Hrm..
 

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Re: Octane gas (scarboroughdub)

Quote, originally posted by scarboroughdub »
you have a 1.8t, the knock detection is very intelligent, it can pin point knock down to each cylinder.
what im trying to say, you can run 87 octane just dont expect any performance as the ecu will retard timing to prevent the knock condition from happening.

moral of the story run 91octane.
 

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Re: Octane gas (mgm)

Quote, originally posted by mgm »
with all the price increases, it "hurts" my wallet everytime I fill up the tank at a higher price

So when the price of gas jumps up you feel it in your pocket? umm take the ****in bus dude, stop bitching like a little girl. If I have to pay $20 more a tank then I will because I get more out of my thirsty vr then anything $20 can buy me... well if a BJ was $20 maybe.
 

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Re: Octane gas (beatmilk)

Quote, originally posted by beatmilk »
I would usually run 91, but I just took my cam and chip out so now it's 87

it runs with out those parts?
 
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