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Does anyone run lower ocatane fuel?

Supposedly the GTI will run fine with lower ocatane fuel with "reduced performance". The first VW in a long time that doesn't always want the expensive gas. I still put the 92 octane in mine all the time, even though the majority of my driving is in traffic with *very little* need for performance. I could just put it in for autocross, but I'm still suspicious.

Anyone run the lower octane with no knocking or problems?
 

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Re: Does anyone run lower ocatane fuel?

I have run both 87 and 89 octane fuel in my Fast. I didn't notice any performance variation. My fuel economy was the same. I do mostly highway driving and use cruise control to avoid getting a speeding ticket. In fact, I got my best fuel economy so far on I-90 between Syracuse and Albany using 87 octane with the cc set at 65; 42mpg!

I can't say whether or not this will affect the engine over an extended period of time. If anyone else knows about this please advise.
 

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Re: Does anyone run lower ocatane fuel?

Man, the I-90 through upstate NY was just buzzing with speed traps last time I went through there. And apparently they measure your speed from the air too.

I would never put 87 in my engine, not even with my old car. I did use 89 when I first got the car though, cause gas prices were so high and I did notice a performance difference. I use only 91 now.
 

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Re: Does anyone run lower ocatane fuel?

I ran 87 for the first oil change and then when the gas prices came down I have started to upgrade to 89. I feel that the car runs better on the higher octane fuels. I did notice a little bit more knock from the 87 octane fuel than I do from the 89 at idle. At speed on the highway there really isn't much of a difference though. The cleaner fuels are also a plus because you get fewer deposits. If I had the choice I would use 91, but for some reason the grades that we have in Texas are 87, 89, and 93. Anyone know the explanation for this one?
 

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Re: Does anyone run lower ocatane fuel?

MattMan said:
The cleaner fuels are also a plus because you get fewer deposits. If I had the choice I would use 91, but for some reason the grades that we have in Texas are 87, 89, and 93. Anyone know the explanation for this one?
A common misconception about octane... A fuels octane rating merely describes the fuels ability to resist spontaneous combustion under compression. Octane has no relationship to the energy potential of a fuel. 91 octane rated fuel can withstand higer pressure before spontaneously combusting than can 87 octane rated fuel. Octane rating also has no bearing on the cleanliness of a fuel and has no impact on mileage unless you are running an octane below what your engine was designed to run.

The octane rating scale is a percentage ranging from 0% to 100%. In the United States there are two methods used to calculate the octane rating of a fuel, one being tested with the engine running under load and the other being tested while the engine has no load (at idle, or free-running). The numbers you see on the pumps are an average of these two rating methods added together and then divided by 2.

Newer engines are designed to operate at higher compression levels (or custom ignition timings) and as such, require fuel with a higher amount of the hydrocarbon atom known as octane (C8H18). The refinement of the fuel and the process of increasing the octane requires more complex processing methods the higher the desired octane rating of the fuel, and as a result, the cost to produce higher octance fuel is higher than the costs to produce lower octane fuel.

Ideally, you should never run fuel with a higher octane than called for by the manufacturer as this is just wasted money with no return on on investment. The reverse is not true however since running a lower octane fuel in an engine that requires a higher octane fuel can decrease engine efficiency by prematurely combusting (engine knock is a result of this) on the compression stroke of the piston which can rob you of the full power you could achieve at the optimal ignition point (the apex of the compression stroke).

Hope this clears up any misconceptions about what octane is and isn't.
 

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Re: Does anyone run lower ocatane fuel?

That is really good information. Lots of people talk about how much 'faster' their car is on higher octane fuel. But, unless your car is set up to run on that higher octane fuel, there will be no benefit to using it. I think it is just their imagination that they are going faster. Try running a blind test and see if they notice. Another instance is when someone slips a K&N filter into their car and says it makes their car so much faster. That's total cocky-pock. Any gain in power by the swapping of a filter would be negligible by the time it reached the rear wheels, and certainly undetectable by human senses. However, you may notice a very slight increase in fuel economy over time.
 

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Re: Does anyone run lower ocatane fuel?

Wouldn't the fact that it's intended to run under higher pressure make it "better" for a turbocharged engine? I don't know, but I can notice a difference with 91 as opposed to 87. Not just in power, but my engine also "sputters" less when idle.
 

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Re: Does anyone run lower ocatane fuel?

Thalo, I think the misconception is that an engineer designs an engine with an intent to run higher octane. The engineer designs the engine so that the engine has the potential for better performance. That extra performance comes with the price of having to feed it better fuel. A fat-ass is not designed as well as a long-distance runner. A long-distance runner is designed to run a marathon, but he/she needs better fuel to get to the finish line faster.
 

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Re: Does anyone run lower ocatane fuel?

Whoopmeister has it dead on. As far as the GTI goes, it calls for 91 octane for best performance, so the engine is designed for higher octane fuel. However, for the first time, VW claims running lower octane fuel is acceptable, with "reduced performance".

For older engines calling for high octane, running lower octane could actually damage the engine (over time).

Presumably, the computers are now technologically advanced enough to know the fuel is lower octane, and adjust everything so it is not damaging.
 

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Regular unleaded fuel?

Hey all, I'm new to the site and I hope I'm not starting off on the wrong foot by asking a stupid question. I'm looking into getting a GTI very soon and was just looking online at beepbeep.com. I was reading the review for the 2006 GTI and came across an interesting statement; " While the car operates on regular unleaded, premium fuel is recommended to achieve maximum power levels."

I know the GTI requires Premium Unleaded fuel and wasn't sure how accurate the statement was. If for some reason it is true it's a plus for me, only because if the price of premium skyrockets I won't go broke. Any feedback would be great. Preferably fact. Thanks.

-Tom
 

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Re: Regular unleaded fuel?

Relentless said:
Hey all, I'm new to the site and I hope I'm not starting off on the wrong foot by asking a stupid question. I'm looking into getting a GTI very soon and was just looking online at beepbeep.com. I was reading the review for the 2006 GTI and came across an interesting statement; " While the car operates on regular unleaded, premium fuel is recommended to achieve maximum power levels."

I know the GTI requires Premium Unleaded fuel and wasn't sure how accurate the statement was. If for some reason it is true it's a plus for me, only because if the price of premium skyrockets I won't go broke. Any feedback would be great. Preferably fact. Thanks.

-Tom
Hey Tom,

First off welcome to the board. To be honest with you the difference from regular to premium at best may be 4 to 5 whp. The only down side to regular fule is that you are going to piss off your fast. I understand the gas issue pretty well I went from a 2002 Expedition to 2006 GTI.
 

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Re: Regular unleaded fuel?

Relentless said:
Thanks, I didn't think the difference would be very drastic to tell you the truth. I appreciate the info.

Would running regular over extended periods harm the engine?(say if i only ran regular)
You will not really cause any damage except maybe dirty fuel injectors.
 

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Re: Regular unleaded fuel?

07FASTGTI said:
i run the highest octane on the gti. if you look on the inside of the gas cap it even tells you it has a recommended octane of like 95 i think. or maybe 92 not sure...
That's dependent on where you're at. The sign says to use 95 RON. In the USA we rate our fuel by (R+N)/2. The MkV GTI recommends 91. Anything over this is throwing money away unless you have the car chipped and tuned to make benefit of the extra octane.
 

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Re: Regular unleaded fuel?

I thought that lower octane fuel could lead to knocking problems due to predetonation in turbo charged engines. I don't know if this engine is efficient enough for that to happen, as this is the first car I have ever owned with a turbo, but I know a little about engines. Am I right?
 
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