Trying to learn a little more on pump e85/flex
Thread Starter
Joined: Mar 2011
Posts: 3,699
Likes: 168
From: Wilmington, DE
Trying to learn a little more on pump e85/flex Running pump flex on my next build. I'm curious if the octane base that is used can legally vary. From what I gathered before I made the decision to run more compression than pump 93 can support, unleaded with an E content of 55-60 is all you need to support 14 or even 15:1 to 1 compression. E60 pump is basically the same as E85 pump. It doesn't really matter once E content is above 50.
I don't know anything really about what base they use tho or how they even "generally" make pump flex fuel, and googling isn't shedding much light on what I'm looking for.
i saw somewgere that soneone mentioned the manufacturer can cut the E with much lower octane rated unleaded, down to the low 80s in octane rating at r/m+2. How true is this? When the companies make regular unleaded, can they make a low octane on purpose just to cheap out and use it for other fuels not regulated? When gas is made, is there an octane rating that it naturally has? Could company A in theory make their pump flex fuel using say unleaded that has a rating of 82 octane, vs company B that uses say 86-87 octane?
I don't know anything really about what base they use tho or how they even "generally" make pump flex fuel, and googling isn't shedding much light on what I'm looking for.
i saw somewgere that soneone mentioned the manufacturer can cut the E with much lower octane rated unleaded, down to the low 80s in octane rating at r/m+2. How true is this? When the companies make regular unleaded, can they make a low octane on purpose just to cheap out and use it for other fuels not regulated? When gas is made, is there an octane rating that it naturally has? Could company A in theory make their pump flex fuel using say unleaded that has a rating of 82 octane, vs company B that uses say 86-87 octane?
On The Tree
Joined: Feb 2022
Posts: 196
Likes: 72
From: Grand Rapids, MI
I don't think octane is regulated with pump ethanol, just the content is regulated which in most cases cannot be below e55 I think.
Yes gas station do cut normal ethanol with lower octane gasoline to get 87 or 88 octane. There is a station near me that does it. They advertise it as like e30 or something. This same station also sells true e85 all year round. They have the highest ethanol percentage in the state. The owner of the station also owns One Ethanol...
Yes gas station do cut normal ethanol with lower octane gasoline to get 87 or 88 octane. There is a station near me that does it. They advertise it as like e30 or something. This same station also sells true e85 all year round. They have the highest ethanol percentage in the state. The owner of the station also owns One Ethanol...
Thread Starter
Joined: Mar 2011
Posts: 3,699
Likes: 168
From: Wilmington, DE
im more curious about the bases that are used. the e content can be measured very easily, but it doesnt matter if it has 60% E if they are mixing it with unleaded rated at like 80-82 octane. thats kinda what im trying to gain knowledge of
Thread Starter
Joined: Mar 2011
Posts: 3,699
Likes: 168
From: Wilmington, DE
I don't think octane is regulated with pump ethanol, just the content is regulated which in most cases cannot be below e55 I think.
Yes gas station do cut normal ethanol with lower octane gasoline to get 87 or 88 octane. There is a station near me that does it. They advertise it as like e30 or something. This same station also sells true e85 all year round. They have the highest ethanol percentage in the state. The owner of the station also owns One Ethanol...
Yes gas station do cut normal ethanol with lower octane gasoline to get 87 or 88 octane. There is a station near me that does it. They advertise it as like e30 or something. This same station also sells true e85 all year round. They have the highest ethanol percentage in the state. The owner of the station also owns One Ethanol...
Thread Starter
Joined: Mar 2011
Posts: 3,699
Likes: 168
From: Wilmington, DE
so let me ask this, say i have unleaded at 83 octane with 0% E. i also have 89 octane with 0% E. if i were to mix say say 5 parts of straight ethanol to 1 part 83 octane, and the same with the 89, how much more "stable" will the 89 be? the only reason why im asking these questions is my next n/a build will be somewhat approaching the limits of pump flex/e85 and just trying to make sure that i have enough of a buffer built into everything since we will be running a pump product that will not be as consistent as stuff from a barrel. i assume that its one of those things where in theory the octane rating of whatever is thrown into the ethanol mix really doesnt mean a whole lot power/compression wise as long as the E content is >60%.
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I believe Ethanol is cut with 87 octane to get to desired alcohol content. If it was cut with 93 octane, the overall octane increase is 1-2 points. E50 is 102-104 octane, E60 is 104-106 octane, E85 is 107-109 octane. The 2-point variance is based on being cut with 87 or 93.
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