Premium gas and ethanol

This is for the folks that think they can get premium gas that is ethanol free. As I have replied to several of these posts ethanol is often used as an octane booster. Ethanol free gas threads are common on boating and fishing forums. The one station near me that sells ethanol free only has it in regular grade and here is why:

Originally Posted By: Anchorman
92 octane has substantially less ethanol than 87. Since learning this I only use 92 in my boats, ATVs, and small engines.


No it doesn't. In fact, it may have more ethanol in it to boost the octane rating to 92. There are only two states in the US that have waivers to sell ethanol free premium unleaded. Those are Missouri and Montana. Other states may allow for the sale of non-ethanol and ethanol laden fuel side-by-side so the consumer gets to choose, but the areas where it is sold must have "attainment status". Oregon specifically prohibits this practice.

 

Ontario, Canada = Ethanol free premium gas

That's all I run. I get better milage (kilometers).

 

I think you're confusing ethanol with methanol. Ethanol is not a booster. In fact, it has less energy per gallon than straight gasoline. Pure gasoline has a higher energy rating than fuel mixtures like E10. The reasons why Ethanol is used is for emissions. Due to it having less energy (roughly 33% less), it has worse fuel economy.

http://www.eia.gov/tools/faqs/faq.cfm?id=27&t=4

 

doesn't ethanol have an octane rating of like 100 something?

 

Talking south of the border. I know nothing about gas in Canada. I would think no ethanol since they do not have a corn lobby.

 

I was throwing in my .02 .... wait a sec, we don't have pennies anymore here either!

 

Pure ethanol does have a higher octane rating, but the energy/gallon is much lower than gasoline. It also is extremely bad for engines not built for more than 10% ethanol blended fuels. They never mix over 10% ethanol, so 91+ octane will still have the same ratio of ethanol as 87. They don't mix ethanol in to boost octane, unless you're in the E85 territory. They mix it for emissions purposes.

 

Shell 91 V Power in Canada is ethanol free

 

Like every other premium 91 in Canada... as mentioned earlier....

 

Thats not true though ^

oh wait

That's not true though .... ^ .....

 

Yes ethanol has less energy per volume than straight gasoline. But a fuel's octane rating is independent of its energy content per volume. Burning high octane gasoline does not always translate to more power than regular gasoline. It might, and it might not. Depends on the engine design and engine management system.

"High octane" simply means the fuel has more resistance to self-ignition under high compression. So high-compression engines or forced induction engines usually require high octane, and have a high output. The important point being, it is the high compression (along with the required high octane) that allows the engine to create more power, not the energy content of the fuel. Regular gas actually contains slightly higher energy content *per volume* than premium, because premium requires more additives to get the higher octane. Those additives which increase the octane typically contain less energy per volume, reducing the overall energy content of the premium grade.

For example, ethanol has far higher octane than premium gasoline, but has far less energy content per volume. So ethanol is in fact an octane booster even though it reduces the energy content per volume.

Yes, pure ethanol is about 99 octane (average R+M)

 

for the shitshow and eventual knowledge i'll get today

 

right beside ya. theres gotta be a oil man here that deals with this subject as his job.....

 

The Pure gas station near my work sells ethanol free 91 octane, which is what I run in my dirt bike, ATV, & small engines. If I need fuel in a pinch, I buy 93 with ethanol and then poor in a few ounces of marine Sta-bil.

 

They never show up. Instead you get nonsense like "the higher the octane, the purer the gas" or "mixing in 10% of something with a higher octane doesn't affect octane." followed by opinions backed with advertising brochures from puregas.com. It's like groundhogs day.

 

There's a station about a half hour from me with 91 ethanol free. Truck likes it a lot, but it's too far out of the way.

 

I stand corrected. It is a booster. The only thing is that 91 octane (ethanol free) will give you better mpg than blended 91.

 

I am so glad there is a new thread on fucking gasoline and octane ratings.

How dare Anchorman say that! We should definitely start a new thread on the subject quoting him in the original post. I am sure wherever he said it was not the place to discuss it and new thread just for the quote is truly required. Good work OP!

 

sorry but ethanol + gasoline is an octane booster.

less energy = less tendency to explode at cylinder pressures (dieseling) = lower octane

Best estimates of the actual octane rating of pure ethanol place it at about 100 octane. but you cannot
actually measure the octane of pure ethanol, you can only measure the resulting octane of adding ethanol to gasoline.

While a little alcohol can bump octane by a few numbers, twice as much alcohol does not result in twice as much octane increase.

cliff notes: it boosts octane


http://www.racegas.com/article/11

 

Just trying to clear the air a little bit on misconceptions about premium. I guess in NC 91 is not considered premium. I always think about the Tacoma forum when I see posts about gas on the fishing/boating forums.