Higher octane for better mileage? - Page 2 - Fuelly Forums

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Old 03-28-2016, 07:38 PM   #11
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The unusual part is the Regular with no ethanol.
87 octane E10(10% ethanol) has ethanol that is 114 octane. To balance the 114 octane ethanol in E10, the gasoline molecules have to average 84 octane. To raise octane by 3 points, just buy 87 octane, E0, which has no ethanol AND ALL THE GASOLINE MOLECULES ARE 87 octane. In my last 5 low 87 octane, low compression ratio (9:1 to 11:1) gasoline engines, E10 mpg compared to E0, dropped 8%, 8%, 8%-7%, 7% & 5%.

Yeah, adding just 10% ethanol to E0, drops mpg that much. 114 octane ethanol needs high compression ratio (16:1) ethanol engines to extract ethanol energy. 87 octane, gasoline engines can't do that efficiently, but work efficiently with 87 octane E0.
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Old 03-29-2016, 01:06 AM   #12
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Thank you.... interesting results.
I'm definitely gonna experiment with my car.
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Old 03-29-2016, 05:44 AM   #13
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For around here. The unusual part is the Regular with no ethanol.
Now the Premium. Many stations advertise no ethanol in the Premium. Why? Those who buy Premium. If there is ethanol in it. They throw their terrible two's fits and all.

I burned mid grade in my last car. The reason was, when gas prices were high. The mid grade was the cheapest, period. I did notice that car had to make adjustments going from regular to mid grade or back. Took it the better part of a tank to make those adjustments.
Where is here?
Depending on subsidies and location, the ethanol in the mid grade could be what made it cheaper than the straight gas of regular and premium.

With improving sensors and computers, the cars should be adjusting to fuel blends faster.
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Old 03-29-2016, 04:10 PM   #14
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Here is the Black Hills of South Dakota.
I did find two stations with much better price on regular E0. ... 203 and 197.... lookin' good. ..
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Old 03-30-2016, 03:11 AM   #15
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Undoubtedly, the ethanol is what makes the mid grade cheaper.
Those prices I posted. They are in comparison to mid grade with ethanol up to 1.87 now. Not far from that.

I remember talking to people who had vari fuel vehicles. They could use the majority ethanol in their vehicles. I think it's 85% ethanol? Called E85? They said that it was much cheaper. But the loss of mileage offset the cost. Also their vehicle didn't run nearly as good.

Take that to the addition of ethanol. There are different amounts. Have to be careful. Can be 5, 10, 15%? Depends on the station. Where I get mine, they don't openly show it. They just make a big deal out of being "top tier" gasoline. I need to find out. If just for interest sake.
Going through this. In the past I haven't really paid much attention. Am getting oriented here. Also, I'm sure, I'll end up with the regular E0. Am definitely going to fill that the next tank. Counting on gaining mileage.
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Old 03-30-2016, 04:13 AM   #16
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Researching....
In Rapid... all the regular E0 is 85 octane.
Have noticed other towns in this state claiming regular E0 at 87 octane?
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Old 03-30-2016, 05:46 AM   #17
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Is the elevation there high enough to warrant 85 octane? If so, it should be fine as long as you fill with 87 before heading for the low country.

E85 will result in lower fuel economy, but should increase power. At least one of the posters at a Sonic forum switched to E85 for the power. The 1.4L turbo is an alcohol sensor shy of being flex fuel. The E85 fuel maps are just locked up in the ECU.

If premium gas on a window sticker didn't cost any car sales, flex fuel engines could do better on E85 with a higher compression ratio to take advantage of ethanol's high octane.

The EPA, at the behest of ethanol producers, is trying to push the E10 many places have to E15. The car and oil companies have pushed back, but newer cars are being made E15 safe.

The law that brought upon the ethanol mandate was written with two assumptions in place. One was that E85 would have become more widely available for flex fuel cars. I had a Ranger for years before a nearby E85 station opened in out of the way Philly.

The other assumption was that gasoline demand would remain the same or grow. It has dropped with more fuel efficient cars being put on the road. With the mandate stating a set amount of gallons of ethanol to be mixed in the gasoline, less gas means a higher percentage of ethanol to meet that number.

E7 is all that is needed for replacing MBTE, but oxygenated fuel is really only needed for carbeurated engines. Considering the number of older cars on the roads, E15 is just too much.

We should have an open fuel law that also allows methanol to be used instead of ethanol. It can be made cheaply from natural gas, which in turn could be made from excess renewable electricity, water, and carbon dioxide.

We should also increase our regular octane, and switch from AKI to RON for it. It will reduce manufacturer costs since that is what most of the driving world uses, and allow the introduction of more efficient engines.
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Old 03-30-2016, 06:12 AM   #18
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Our elevation in Rapid is 3200 feet. The prairie out from here is about the same. Takes a long time to reach low elevation from here. Sioux Falls, which is about the same distance as Denver, but different direction. It's 1470. Gillette Wy, to the west, is 4500. The highest elevation town in the Hills is 5300 feet.
Not sure what you mean on low elevation? Or is this high enough?

As far as I know. The only station selling the E85 here is the flying J truck stop.
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Old 03-31-2016, 05:36 AM   #19
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Octane is a measure of the gasoline's resistance to knocking. Knocking occurs from too much heat, which is mostly created by the pressure of compression. Higher compression ratios means higher cylinder pressures, and the reason high CR engines need higher octane fuel for full performance and efficiency.

At high er elevations, the air is thinner. This means there is less of it per cylinder volume. So the pressure when compressed is lower than when the engine is at sea level. This means a naturally aspirated engine can can safely use an octane lower than the US regular standard of 87 octane.

The 85 octane at those elevations might return the same fuel economy as 87. If so, use it if it is cheaper. Taking a car filled with 85 to a low elevation risks knocking though. I don't know at which elevation 85 octane becomes too low. I do think the knock sensors and ECU will protect a modern engine if that elevation point is past. But that is a call for the car's actual owner.
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Old 04-04-2016, 08:39 AM   #20
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I've always found that running No Ethanol fuel nets me 2-3mpg better than ethanol fuel. My 95 will pull an extra 2-3 mpg from 91 no eth over 87 eth fuel while feeling more powerful, but the extra $.30-60 a gallon isn't really worth it.
On a newer vehicle designed for ethanol fuel, you likely won't notice much difference.
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