fuel quality and ethanol

[bonjo]

since it first introduction and now creeping in in higher concentration like a cancer, I have been wondering is it also allowing petrol producers to use lower & cheaper octane fuel and bump it up by adding ethanol while charging the customer the same or higher price

 

[kschachn]

Since EtOH has a higher octane rating than gasoline, and fuel is sold at a specific octane rating, then yes if you increase the concentration of the ethanol you would use a base with a lower octane rating.

 

[rstcso]

Or keep the base gasoline the same but use less per gallon. If ethanol wasn't so highly subsidized, it wouldn't be less expensive.

In this Engineering Explained video, Jason goes through the switch to ethanol in gasoline and why he's no longer a believer in the benefit of using it. It's a few years old, but I don't remember seeing him post a rebuttal to his own video, which he will do when he thinks appropriate.

 

[dubber09]

Engineers don't believe, they base conclusions on data and test results.

 

[rstcso]

Engineers don't believe, they base conclusions on data and test results.

My words, not his.

 

[JohnnyG]

There are only two grades of gasoline, but the base octane can vary a bit. All other grades are blended from those two, with ethanol considered in the final product.

 

[y_p_w]

There are only two grades of gasoline, but the base octane can vary a bit. All other grades are blended from those two, with ethanol considered in the final product.

I think it's a lot more than that. I've heard it described as "buckets" of this or that and then the refinery blends them together to meet the requirements for finished fuel. But there are certainly industry standards. The most commonly traded commodity fuel in the US is RBOB, meant to be blended with 10% fuel ethanol in order to meet the 87 AKI requirement for regular unleaded in most of the United States.

The original post was obviously meant to be inflammatory. The quality of fuel isn't necessarily better or worse with ethanol, MTBE, or whatever. But we're dealing with an industry where currently ethanol is the cheapest and most effective way to increase anti-knock properties. There are people with flex-fuel vehicles who go out of their way to get E85 just on the basis of performance gains (at the expense of MPG).

 

[JohnnyG]

I think it's a lot more than that. I've heard it described as "buckets" of this or that and then the refinery blends them together to meet the requirements for finished fuel. But there are certainly industry standards. The most commonly traded commodity fuel in the US is RBOB, meant to be blended with 10% fuel ethanol in order to meet the 87 AKI requirement for regular unleaded in most of the United States.

The original post was obviously meant to be inflammatory. The quality of fuel isn't necessarily better or worse with ethanol, MTBE, or whatever. But we're dealing with an industry where currently ethanol is the cheapest and most effective way to increase anti-knock properties. There are people with flex-fuel vehicles who go out of their way to get E85 just on the basis of performance gains (at the expense of MPG).

After 35 years in the industry, I've never seen a "bucket" of anything being added to gasoline. Now, some niche markets, like racing fuel from specific sources do exist, but these are not normally "pipelined" commodities. And California is a whole other story, which is why refineries are closing there.
Unless those buckets are REALLY big, like thousands of barrels, it wouldn't make economic sense.

Blending racks are a thing, as well as computerized control at the terminal, that's just the way it's done.

Let's hope MTBE is LONG gone btw. A friend of mine would haul tanker loads of that stuff out in Colorado years ago. Passed out a few time from the fumes (yes, while driving) and the loads would always come up short. Come to find out it was actually escaping through the solid aluminum shell of the tank truck. No leaks!

 

[JohnnyG]

since it first introduction and now creeping in in higher concentration like a cancer, I have been wondering is it also allowing petrol producers to use lower & cheaper octane fuel and bump it up by adding ethanol while charging the customer the same or higher price

Except this happened 20 -25 years ago. Two grades of gasoline, 84 octane and 91 octane. blending AND ethanol does the rest.
Unless the refiners move to 82/83 octane for RBOB and 89/90 for premium, with 15% ethanol, I don't see it making much sense.
Octane does cost money at the refinery end.

 

[y_p_w]

After 35 years in the industry, I've never seen a "bucket" of anything being added to gasoline. Now, some niche markets, like racing fuel from specific sources do exist, but these are not normally "pipelined" commodities. And California is a whole other story, which is why refineries are closing there.
Unless those buckets are REALLY big, like thousands of barrels, it wouldn't make economic sense.

Blending racks are a thing, as well as computerized control at the terminal, that's just the way it's done.

Let's hope MTBE is LONG gone btw. A friend of mine would haul tanker loads of that stuff out in Colorado years ago. Passed out a few time from the fumes (yes, while driving) and the loads would always come up short. Come to find out it was actually escaping through the solid aluminum shell of the tank truck. No leaks!

I meant that the refinery distills different streams of fuel that might be 85/87/89/91/93/95 AKI. I remember seeing quotes of an article from Sport Compact Car magazine about why California was turning to 91 AKI for premium unleaded when it was traditionally 92. I remember the word bucket, but it was more about blending stuff and placing it in a "bucket".

This is one version of the article as quoted:

https://www.m3post.com/forums/showthread.php?t=737734​

You see, when crude oil is refined into gasoline, the refinery doesn't have all that much control over what comes out. Crude oil is full of all kinds of stuff, and a refinery simply separates it, sorting all the iso-this and hepta-that in order of density. The really heavy stuff, like tar, is near the bottom, while the really light stuff, like butane, is near the top.​

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Somewhere in the upper ranges of the stack are the components of gasoline. There are between 10 and 15 different blend stocks, each with a different octane rating, which are mixed together to make gasoline.​

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The crude oil being used and little else determine the amount of each blend stock available for mixing. Generally, if you just dump all the blend stocks into a bucket, you end up with something around 88 or 89 octane. If you're selective and only mix the good stuff, you can make 92, 93 or even 95 octane. But once you take out the good stuff, you're left with crap--something like 85 octane. Then you have to leave enough good stuff in the bucket to bring this pee-water up to at least 87 octane. This limits the amount of 95-octane gas you can make. If you make 93-octane premium instead, you use up less of the high-octane stocks, allowing you to make a higher proportion of premium fuel.​