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Discussion Starter · #1 ·
I got right at 30 mpg driving normal on the tank that ended last Monday. I had been reading up on the octane threads and did a few small mods (40 psi in all 4 corners, free !baffle cai, !spare, and of course the 90 octane) in addition to a renewed focus on hypermiling and thus far have seen about 38 mpg on the in-car computer system - which typically translates to approximately the at the pump value +2 mpg. So, 29.7 to ~36 for basically free. I've even still romped on it a few times, what with the CAI and the premium the car feels much more responsive than it did when I test-drove it. I think I may even be able to take a stock Focus (LOL).

If not for the stories of guys blowing out their clutch with the Trifecta tune I would probably be going for that shortly but, as it sits, I'm pretty happy. I just need a way to secure my damnable bazooka tubes in the trunk!
 

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Not to sound like a "dick," but you have to pay more for higher octane fuel. You're not getting those extra MPGs for free ;)

But I have been hearing a lot about higher octane getting you a few extra MPGs with the Cruze, I think it's because of the turbo. I'm getting an average of 30MPG (avg 32 on the DIC) with like 60%hwy and 40%cty driving.
 

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Not to sound like a "dick," but you have to pay more for higher octane fuel. You're not getting those extra MPGs for free ;)

But I have been hearing a lot about higher octane getting you a few extra MPGs with the Cruze, I think it's because of the turbo. I'm getting an average of 30MPG (avg 32 on the DIC) with like 60%hwy and 40%cty driving.
For the $2 extra a tank, it's sometimes worth it. It's worthwhile to me, as I drive enough to make less frequent fillups a $2 luxury.
 

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Where do you get the 86 and 90 octane fuel? Most places I go to have 87 89 and 93. I know when I traveled out west I saw 85 or 86 octane but not in Cinti unless Sunoco carries it.
 

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But I have been hearing a lot about higher octane getting you a few extra MPGs with the Cruze, I think it's because of the turbo. I'm getting an average of 30MPG (avg 32 on the DIC) with like 60%hwy and 40%cty driving.
It is flat out not true nor is it backed up by scientific evidence. Octane does not change fuel consumption. I ran 87 Octane for a few tanks and 91 for a few tanks when I first bought the car in summer and... no change. 87 Octane and 93 Octane have the same BTU if their ethanol contents are the same.

Now, the car does gain a few horses with higher octane.. less knock and / or advanced timing. That can translate to better MPGs to drivers that like to jackrabbit their cars because it will accelerate more "satisfactory" so they flog the accelerator less.
 

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It is flat out not true nor is it backed up by scientific evidence. Octane does not change fuel consumption. I ran 87 Octane for a few tanks and 91 for a few tanks when I first bought the car in summer and... no change. 87 Octane and 93 Octane have the same BTU if their ethanol contents are the same.

Now, the car does gain a few horses with higher octane.. less knock and / or advanced timing. That can translate to better MPGs to drivers that like to jackrabbit their cars because it will accelerate more "satisfactory" so they flog the accelerator less.
The higher octane might get some folks higher MPG due to less knock being present. Also, less knock = more timing advance, which means less fuel being used to make the same power. For somebody who's gentle on the gas, getting the most timing advance possible is synonymous with less fuel being used. It works both for power and MPG. Whether one's car sees better MPG or not depends very much on driving style.
 

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There's an article worth reading in the April 2012 issue of ROAD & TRACK, "Premium Fuel Futures--A primer on high-test gasoline: Is it for you?," pages 84-89, by Dennis Simanaitis (their resident engineering editor).

It's well worth reading. Here are some 'tid-bit' quotes to pique your interest:

"Neither is indicative of MBT, Minimum advance for Best Torque, the optimal ignition setting for a particular combination of engine speed, load -- and fuel."

"Pure and simple, a gasoline's octane rating is a measure of its resistance to knock as compared to a particular pair of hydrocarbons."

• "In fact, depending on its blending, a premium fuel may actually contain less energy per unit volume than regular."

• "However, its [premium] potential for producing more power and enhanced mpg goes back to MBT and the knock sensor. And with less than Best Torque, there'll be less performance and an mpg hit."

• "Modern knock-sensed ignitions seek MBT timing and thus, at least in theory, profit from added octane. Some, though, have preset ceilings beyond which they won't advance."

• "Ethanol, used as an extender in much of our gasoline, is also an octane enhancer. Blended at a minimum of around 6 percent, its pump stickers state "up to 10 percent ethanol" to account for refinery optimizations of catalytic cracking, isomerizing, alcohol enhancement and other techniques."

• "Detergents reduce carbon buildup, all the more important these days with high-pressure direct-injection hardware."

• "Antioxidants improve the storage and tank life."

• "Corrosion inhibitors and dyes are also added."

• "As already noted, premium gasoline may actually contain less specific energy than regular, though this is more than countered by exploitation of its higher octane."

• "EPA's certification fuel is indolene, a standardized test gasoline free of additives."

• "Factoid: Premium fuel is good for a catalytic converter."

• "Chevrolet Volt--This engine produces 84 bhp--and requires premium fuel. A 10.5:1 compression ratio and commensurately more spark advance are said to enhance efficiency to the tune of 5-10 percent better fuel economy. Another payoff is premium's more extensive additive package, among them more antioxidant if the car is only infrequently run beyond its battery range."
 

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Discussion Starter · #10 ·
37.5 @ the pump, 38.3 on the computer when I filled it up. For intake cai I just ran a 4" dryer vent to the foglight area from the airbox. And previous tank netted 29.9 mpg at the pump. Only huge driving change is coasting down in gear vs before when i would do it in neutral.
 

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37.5 @ the pump, 38.3 on the computer when I filled it up. For intake cai I just ran a 4" dryer vent to the foglight area from the airbox. And previous tank netted 29.9 mpg at the pump. Only huge driving change is coasting down in gear vs before when i would do it in neutral.
You're telling me you bumped from 29.9mpg to 37.5mpg by running a dryer vent from the fog light to the airbox?
 

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37.5 @ the pump, 38.3 on the computer when I filled it up. For intake cai I just ran a 4" dryer vent to the foglight area from the airbox. And previous tank netted 29.9 mpg at the pump. Only huge driving change is coasting down in gear vs before when i would do it in neutral.
I have found with premium fuel that coasting in gear causes the fuel shutoff DEC function to happen far more often than with regular fuel. My scangauge reads 9999 mpg instant when the fuel shutoff is activated.

A little over 2 mpg average increase pays for the cost of premium fuel at my current average mpg.
 
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