93 w/10% ethanol or 91 pure?

[BladeGT]

So in my small city in WI, I only have one gas station that sells 93 and it contains 10% ethanol to achieve its oct. rating. Every other gas station in town has 91 pure gas as premium. Which would be the better fuel choice here? Both are "top tier". 93 w/eth is Mobil and the 91 Im considering are Shell and Kwik Trip. Thanks!

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[EFI]

For most power, E10 93 for sure. For better fuel economy, pure 91.

 

[BladeGT]

For most power, E10 93 for sure. For better fuel economy, pure 91.

Yeah im looking for power gains here, f gas mileage... You gotta pay to play. My only concern is the ethanol.

 

[RenegadeRedneck]

My stock 2011 likes 94e10 over 91 for cold starts in Calgary winters. Idles smooth as silk on 94, rough every few days on 91.

 

[BmacIL]

Yeah im looking for power gains here, f gas mileage... You gotta pay to play. My only concern is the ethanol.

What is the concern? I'm running flex fuel with my tune and it's glorious and cheap.

 

[BladeGT]

What is the concern? I'm running flex fuel with my tune and it's glorious and cheap.

I remember reading somewhere(cant remember source), that running gas w/ethanol was inferior to pure gas. Something about eth. being heavier or lighter than H2o and causing moisture build up in the gas tank during evap. If that makes any sense. That and varnishing?!?

 

[BmacIL]

I remember reading somewhere(cant remember source), that running gas w/ethanol was inferior to pure gas. Something about eth. being heavier or lighter than H2o and causing moisture build up in the gas tank during evap. If that makes any sense. That and varnishing?!?

Ethanol does absorb moisture faster than gasoline but unless you're letting it (E10 gas) sit for months on end with no stabil, it's not an issue. All modern cars are designed for use with ethanol in the fuel. Ethanol has a lower energy content than gasoline but the octane rating and the resulting timing increase makes up for it.

E85 will have issues if it sits for a few weeks but there's really no need to be concerned.

 

[DarkestHour]

Car is setup from OEM to assume you use E10. If you use 91, the car will just try to target a richer stoich (14.1 instead of 14.7) target and wipe out the majority of any fuel mileage gains.

Ethanol is perfectly fine. Anyone telling you otherwise is ignorant and probably thinks the government wire taps their house.

 

[EFI]

I remember reading somewhere(cant remember source), that running gas w/ethanol was inferior to pure gas. Something about eth. being heavier or lighter than H2o and causing moisture build up in the gas tank during evap. If that makes any sense. That and varnishing?!?

First of all, cars have been running E10 or thereabouts for decades without any issues. Second, do you plan on keeping this car for anywhere near that long?

Don't worry about it.

 

[WildHorse]

94 e10 for sure. Like others have said, don't believe the typical bullshit about e10.

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