Truth about gasoline, ethanol and octane?!

[Mikeez]

Hey guys,

Octane rating is just how much the fuel can be compressed before it explodes and make your car move forward... That means that (e85) has 85% ethanol and therefore the octane rating should be 100 or more. So e85 is better than regular
91 octane rating gas which only contains 10% ethanol or what?

What I learned in chemistry is that ethanol only has 2 carbons, therefore not producing enough energy. Additionally, ethanol is a alcohol family member . Therefore, it will be corrosive for the engine.

So is it better to go unleaded gasoline with no ethanol?

[Khorne]

You need google more than anything else.

Ethenol based fuel is fine to put in an engine it will not corrode it. Because ethenol produces less energy than traditional fuels it requires more to be injected into the cylinder and burned so you'll use more fuel.
The octane rating is how resistent the fuel is to pre detonation, so use a higher octane if you wish to get more power, run more boost, advance timing.

Neither is better overall, each have pluses and minuses use whats best for your application.

[alan.chalkley]

Originally Posted by Khorne

You need google more than anything else.

Ethenol based fuel is fine to put in an engine it will not corrode it. Because ethenol produces less energy than traditional fuels it requires more to be injected into the cylinder and burned so you'll use more fuel.
The octane rating is how resistent the fuel is to pre detonation, so use a higher octane if you wish to get more power, run more boost, advance timing.

Neither is better overall, each have pluses and minuses use whats best for your application.

According to Nulon engineers here in Sydney-
Ethanol is hydroscopic and therefore absorbs water , leading to corrosion within engines.
Special oil is required and more frequent oil changes.

[Fastbrew]

This is why Gale Banks loves diesel. Octane becomes a non issue. Squeeze it until it blows up.

[zkv476]

Ethanol has less specific energy, but its resistance to knock allows as mentioned the ability to run more ignition advance and boost. It's much easier to compensate for less specific energy by injecting more fuel than to advance timing or increase boost beyond what will cause gasoline to detonate.

On a side note, hygroscopy actually doesn't cause corrosion, rather the opposite. Brake fluid is hygroscopic for a reason, it is designed to absorb water that becomes introduced into your brake system through moisture in the air generally, and it actually prevents the water from corroding the brake lines and systems.

[alan.chalkley]

Water inside brake lines boils and is very dangerous , which is why they are flushed and new brake fluid is added under routine maintenance.
This is also why more frequent engine oil changes are needed when ethanol fuels are used.

[cdrazic93]

Originally Posted by zkv476

Ethanol has less specific energy, but its resistance to knock allows as mentioned the ability to run more ignition advance and boost. It's much easier to compensate for less specific energy by injecting more fuel than to advance timing or increase boost beyond what will cause gasoline to detonate.

You're thinking of specific heat. It literally combusts cooler than gasoline does, another reason it prevents knock. but yes, pound for pound it has less energy than gasoline. The reason why it produces more is it's ability to withstand much higher cylinder pressures than gasoline. This is also why E85 is worse on MPG than gasoline as well, you need more of it to make a lot of power.

[zkv476]

Originally Posted by cdrazic93

You're thinking of specific heat. It literally combusts cooler than gasoline does, another reason it prevents knock. but yes, pound for pound it has less energy than gasoline. The reason why it produces more is it's ability to withstand much higher cylinder pressures than gasoline. This is also why E85 is worse on MPG than gasoline as well, you need more of it to make a lot of power.

No I did mean specific energy, it is the energy per mass of something :p. Specific heat is the amount of energy needed to change the temperature of something by a degree. Ethanol is actually higher haha, as in it takes more heat energy to raise the same mass of something by a degree.

Originally Posted by alan.chalkley

Water inside brake lines boils and is very dangerous , which is why they are flushed and new brake fluid is added under routine maintenance.
This is also why more frequent engine oil changes are needed when ethanol fuels are used.

It's not as dangerous as brake components rusting, corroding, seizing, and potentially disintegrating. Absorption of water prevents the worse of the two evils. DOT5 (not 5.1) brake fluid is silicone based and is not hygroscopic so it doesn't absorb water, but it's more difficult to bleed, absorbs air, and is incompatible with ABS. Also if there is water that manages to get into the system, it won't prevent corrosion and rusting. I forget the exact reason OCIs are shortened but I believe the ethanol dilutes the oil more easily.

[alan.chalkley]

Or maybe sludges up the oil more easily with rust.

[Mikeez]

Well thank you everyone for the interest in replying. I appreciate everyone's comment and opinion. I will have to search deeper lol!

[Canibalistik]

Originally Posted by alan.chalkley

According to Nulon engineers here in Sydney-
Ethanol is hydroscopic and therefore absorbs water , leading to corrosion within engines.
Special oil is required and more frequent oil changes.

I think you mean "Hygroscopic," as hydroscopic isn't an actual word.


To answer your question though, your best advice was given about third post. Stick to what is best for your application, or better. More octane rating, better power, better/smoother running, and better for performance. I'm not saying go run on race fuel or 100+ octane non stop. Unless you're ballin' and can afford that kind of stuff. I can tell you from previous experience with detonation and spark knock that you don't want to use e85 in a regular unleaded engine...especially not any version of the FT 86. I've owned a WRX with an EJ25, and now my FR-S with the FA20, and would highly recommend at the very least 93 octane rated fuel.

Overall...its fuel...you need it to drive...just pay for it!

[alan.chalkley]

Originally Posted by Canibalistik

I think you mean "Hygroscopic," as hydroscopic isn't an actual word.


To answer your question though, your best advice was given about third post. Stick to what is best for your application, or better. More octane rating, better power, better/smoother running, and better for performance. I'm not saying go run on race fuel or 100+ octane non stop. Unless you're ballin' and can afford that kind of stuff. I can tell you from previous experience with detonation and spark knock that you don't want to use e85 in a regular unleaded engine...especially not any version of the FT 86. I've owned a WRX with an EJ25, and now my FR-S with the FA20, and would highly recommend at the very least 93 octane rated fuel.

Overall...its fuel...you need it to drive...just pay for it!

Thanks! Here in AU , 98 octane fuel is readily available everywhere , so that is only what i use.

[rice_classic]

Originally Posted by Canibalistik

I think you mean "Hygroscopic," as hydroscopic isn't an actual word.

"To describe something that is or like, in function, an instrument for taking images or video underwater such as a hydro scope."

Not technically a word, per se.

If my go-pro is put in a waterproof case for use underwater does that technically make it a (n) Hydro Scope or could I technically describe it as (adj) hydroscopic in function? I'm pretty sure the answers are 'yes' and ''.

[Canibalistik]

Originally Posted by rice_classic

"To describe something that is or like, in function, an instrument for taking images or video underwater such as a hydro scope."

Not technically a word, per se.

If my go-pro is put in a waterproof case for use underwater does that technically make it a (n) Hydro Scope or could I technically describe it as (adj) hydroscopic in function? I'm pretty sure the answers are 'yes' and ''.

Sure you could say that! Just like I could make up a couple thousand other words up and use them in a sentence to try and troll someone on the internet who was just trying to help educate on his terminology.

Hydro Scope is in the dictionary. You're right...clever you, however, "Hydroscopic" is not.

Also, to re-instate the uselessness of any time spent on the argument you made...how would one use e85 to look at objects under water?!