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Discussion Starter #1 (Edited)
First a little about gas.
Because higher octane gas has less energy (lighter density) it actually gets LESS miles per gallon...but more performance...
Shorter hydrocarbon strands for the lighter, and longer for the denser. Gasoline is a regulated mix of hydrocarbon types, in order to burn within a certain specification.

Second, almost all gas is the same, it comes from the same refinery, is loaded into a tanker truck at the same place, and contains the same mix of distillates. The only major difference is a quart can of detergent added to the tanker truck. (5000+ gallons)

Smart says use 95 RON (Research Octane Number). This translates to 90-91 AKI (Anti Knock Index), or (Research+Motor octane)/2), or the number on the gas pump.

91 RON, the minimum Smarts will use, is 87 AKI.

I have use all three grades, regular, mid, and super; and have found that regular gives me the roughest idle, but the best mileage over long highway trips, and 92-93 AKI gives me great power, but poor MPG.
I am splitting the difference and putting in 89, and adding 16 ounces ethanol (E85) to five gallons, or 32 oz (quart) to ten gallons, to boost the octane.
This adds about 2.5% (actually a little less, only 70 to 85% ethanol in E85), and most gas has between 6.9 (Federal minimum) and 10%.

Gripe all you want about ethanol, there is a lot WORSE we could add to boost octane, tetra-ethyl lead (major air polluter), methyl tert-butyl ether (major water polluter), and benzene (cancer).

Ethanol is also an oxygenated fuel, so less tailpipe emissions.

Does this help clear up a few things?
 

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No it does not clear up a few things, and this should not be a sticky

I Keep the Ethanol out of my car as much as I can
The Good stuff here can be had as 100% pure Gas. I know the ethanol cuts my MPG and is a bad way to boost octane.
 

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No sticky...

1. Don't use Wiki for a reputable source. Use it to get the idea but afterwards search elsewhere for reliable information.

2. Ethanol is not good for MPG nor performance. Sure, it increases octane and reduces pollution but it's not the same as 100% pure fuel and sometimes doesn't even come close.
 

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Ok... you quoted a Wikipedia article... that in and of itself is the denial for a sticky...


Manufacturer says put premium in... I'm putting premium in...
 

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If alcohol is so bad, why does a friend of mine use it in his drag racer? His fuel mileage is terrible but he does go fast!
 

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+1 Wdhitch

Wiki is never a reputable resource (ask a professor). If they tell me to put Premium in I'm putting Premium in. Besides, Premium has its own benefits over Regular (reduce engine knock, higher octane, etc.) that I'd gladly fork over 15c more for.

If alcohol is so bad, why does a friend of mine use it in his drag racer? His fuel mileage is terrible but he does go fast!
There's a difference between a drag racer and a production car. The drag racer is designed to run on such fuel.

Often alcohol will eat away at parts of the fuel system and generally is not as combustible as 100% pure fuel.
 

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Discussion Starter #10
Major point was....

Smart says use 95 RON (Research Octane Number). This translates to 90-91 AKI (Anti Knock Index), or (Research+Motor octane)/2), or the number on the gas pump (PON - Pump Octane Number).

Look on the pump next time you fill up, it says "R+M/2"
 

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I hated the mixing of oil and gas on my old 2 stroke machines, and I really don't want to mess with mixing any additives to the gas in my smart.I have found that the local station Premium works pretty darn good for me, I buy 90% of my gas from there. I have tried gas at other locations and didn't get any better results, usually worse. ( it (I tried multiple tankfuls to be sure) The premium I use is rated at 92 (at the pump) and is only a few cents more than regular. Sadly it is 10% but that is about all you can get around here.
 

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I suppose. The car should be timed to fire Premium fuel. Using lower grade fuel might make a very slight difference...
 

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Ok here is a question for the OP

Is the Regular you are putting already 10% ethanol?

If you add a bit of E85 to that just to get to an Octane rating your are upping the % of ethanol.
From the manual


Adding e85 to an already 10% mix is not worth the risk to all the parts of the car that the fuel comes in contact with. You can do damage to those parts, they are not designed to handle more than 10%.

Ill stick with my 100% Gas and pay the extra $1.00 a fill up.
Sounds like cheep insurance to me
 

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Mine likes BP/Amoco 93 premium with no/low ethanol. While I'm sure the engine will run fine on 91/92 per the manufacturer's recommendations, I've tried other stations 91/92 and mileage suffered. I'll keep running 93 and stay in the mid to high 40s for my commute MPG. :)
 

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Some of us don't get the choice of 100% gas - all you can get all over Dallas/Fort Worth is 10% Ethanol. To possibly find 100% gas, I'd have to drive 15-20 miles each way for it, which would not help my weekly mpg at all. If I had to guess, I'd bet that the 10% Ethanol is going to spread to everywhere, not go away. The only two bits I got for this one...
 

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I've yet to find a station in IL. without 10% ethanol :(

I mean I did find ONE, but it was pure 100 octane fuel...(It's close to a boat launch)...
 

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The only non-ethanol gas I found also contains lead. It is for off road and pre-catalytic converter vehicles only, and about twice the price.
 

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Holy crap im more confused then when i started....
Why cant I just pull up to the pump, smile at the SUVs standing there for 30 min, pump my 8 gallons, and leave in less then 5 min without having to do some form of long algebra!
If it gets to the point im doing more to stick it and pump it (go ahead) im going to a bicycle....
Over thinking fail
 
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