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  #13  
Old 02-09-2012, 10:21 PM
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It also could just be the blend of gas. I know stations around here say the may contain "up to" 10% ethanol - but of course they may not. Could be small amounts of water or other issues with the fuel too. I don't think you can say the difference was the octane though.
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Old 02-10-2012, 08:45 AM
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Re: 2012 WK2 Grade of gas

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Originally Posted by SW03ES View Post
Thats totally in your head. Seriously, they have done study after study, using a higher octane gas than what is recommended does nothing for performance.

I won't debate anyones controlled finding.....

But real world applications and certain driving condition do yeild counter intuitive results.

Most of my driving is mountain driving and stop and go driving and the higher torque produced by the higher octane consistently nets me 1 mpg higher average mpg in the evic with the same driving route and same traffic conditions than when I run a tank of 87.

The gas stations I fill up at only offer 87 and 91 or 93 (Texaco or Total formally Esso)

I usually purchase 22 gallons per purchase.
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Old 02-10-2012, 10:44 AM
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Re: 2012 WK2 Grade of gas

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Originally Posted by Jeep_addicted View Post
Most of my driving is mountain driving and stop and go driving and the higher torque produced by the higher octane consistently nets me 1 mpg higher average mpg in the evic with the same driving route and same traffic conditions than when I run a tank of 87.
Thats just not possible. Higher octane doesn't produce higher torque, thats the flaw in your argument. You're not running racing fuel, you're running the same fuel with a slightly higher anti-knock rating, it has no bearing on performance. The same driving route is never the same twice, conditions aren't the same, etc. Ask any mechanic, any engineer, and they will tell you that.

You can believe that if you want, but its just the placebo effect.
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  #16  
Old 02-10-2012, 11:22 AM
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Well, with the caveat that if your knock sensors are causing timing to be pulled then higher octane will prevent that. You could say that you are losing power with lower octane (because timing is being pulled). But that would normally only occur under extreme temps or conditions. There isn't any more energy in 91/93 than in 89.

I know I sometimes notice a huge difference between one tank and another for no particular reason. (I only use 87). Sometimes it seems one station is better but a few weeks later it seems it isnt better any more. Even at a given station gas can vary depending on where they sourced it, how old it was, what blend it is, and how empty the tank was. Just too many variables.
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Old 02-10-2012, 12:57 PM
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Re: 2012 WK2 Grade of gas

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Originally Posted by BManz View Post
You mean 20+hp. It's more like a 6%-8% reduction in power if the engine has a tune to take advantage of a higher octane and you run a lower one. If the change is more than 10-15hp, oh yeah, a car guy like me will feel that on full honk acceleration. While I'm not an engineer, I built, dyno'd and raced a few engine/chassis combos over the years which involved working alongside some powertrain engineers from various manufacturers who were also racers on the weekends and it's what we saw. One of those guys introduced me to this forum as a matter of fact.

This very octane discussion, and torque/horsepower debating, was had many times over beer and brats. The -8% power reduction number matched what we typically saw on dyno testing changing nothing but the fuel and timing to reduce detonation -- I liked trying to build street-gas friendly race engines when money was tight. Modern engines retard timing quickly at the hint of detonation even running the designated octane fuel. So on a hot day while running your engine hard you'll feel a power loss too even running the optimal gas, 87, 89, 91, whatever, as the computer retards timing. It would be a pain to do a controlled test for this on the Grand without disconnecting the fuel tanks, but it'd be interesting.
I meant 10.
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Old 02-10-2012, 05:55 PM
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Re: 2012 WK2 Grade of gas

I only use the best and I get a 10MPG and a 130HP and torgue increase. 87 or 91 LOL!


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Old 02-11-2012, 12:57 AM
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Re: 2012 WK2 Grade of gas

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Originally Posted by CFUSION View Post
I only use the best and I get a 10MPG and a 130HP and torgue increase. 87 or 91 LOL!
You forgot the smoother shifts from the transmission
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Old 02-11-2012, 11:56 AM
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Re: 2012 WK2 Grade of gas

In my experience, running a car designed for 93 on 87 can impact mileage/performance as a result of the retarding of the timing (which keeps the engine from knocking and allows it to still run okay). I had a Passat 1.8T years ago that was noticeably down on power & mileage when running 87 (turbo probably made that worse).

However, the converse - running a car designed for 87 on 93 - really has no impact on performance/mileage at all.
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Old 02-12-2012, 09:15 AM
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Re: 2012 WK2 Grade of gas

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Originally Posted by cfusion View Post
i only use the best and i get a 10mpg and a 130hp and torgue increase. 87 or 91 lol!


lol!!!
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Old 02-13-2012, 12:34 AM
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Re: 2012 WK2 Grade of gas

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Originally Posted by brandont View Post
Well, with the caveat that if your knock sensors are causing timing to be pulled then higher octane will prevent that. You could say that you are losing power with lower octane (because timing is being pulled).
This is true when you run 87 in a vehicle designed for 91+. However, the inverse is not true, when you run 91+ in an engine designed for 87 the knock sensors don't all of a sudden cause the timing to be pushed and cause power to be created that the engine wasn't designed to produce...
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  #23  
Old 02-13-2012, 07:45 AM
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Quote:
Originally Posted by SW03ES View Post
This is true when you run 87 in a vehicle designed for 91+. However, the inverse is not true, when you run 91+ in an engine designed for 87 the knock sensors don't all of a sudden cause the timing to be pushed and cause power to be created that the engine wasn't designed to produce...
That wasn't what I was trying to say. I meant that if you were LOSING power already, then you'd get it back. K
Unlikely you would be losing it in the first place as that only happens in extreme conditions.
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