My stock engine I run 87 octane. Or unleaded. Well there's 89 and 91 options, and then e85? When should I start running higher octanes? And how come a smaller octane like e85 is better?

 

e85 isnt a smaller octane. its 85% ethanol. i dont know its exact octane rating, but its better than 91.

if you start modding i would go with 91

edit: just looked it up and e85 has a octane rating of 105, so its like race gas

 

What upgrades should i put in before running 91? Wouldn't it slow me down without upgrades?

 

You obviously need a tune for this.

and yes if you are planning a tune you might as well do the whole shabang. Air intake, intake manifold, and full exhaust.

Won't net you that many HP though. 20-30 over stock fully bolted.

 

First off, what kind of car do you have?

 

06 cobalt 2.2L.

 

At least bolt-ons and a tune. Running anything other than gas in a stock car isn't going to do anything. Running anything other than gas in a bolt-on car without a tune isn't going to do anything.

E85 takes a lot more than just putting the nozzle in and pumping the gas. You'll need to make quite a few upgrades to the system in addition to tuning, especially on a 2.2. It's only worth it if you're going all-out with a turbo build.

 

Higher octane doesn't even mean higher power. It simply means a higher resistance to detonation or knock. The reason why boosted cars run higher octane is because they are generating more heat and pressure which can easily lead to knock so they need resistance against it. e85 is mainly for high hp builds because it burns cooler and also has a higher octane than any normal gasoline so it is very resistant to knock. However, it takes much more ethanol to run an engine than gasoline which means you will empty your tank faster.

 

I got tuned for E85 in my fully bolted 2.2. It won't do much. My trap times went from 93 to 94 in the 1/4. I used it to see if I would save money on gas, but with the drop in gas mileage if E85 isn't atleast 60 cents cheaper than regular then your losing money.

 

Yeah alcohol isn't as efficient of a fuel as gasoline. Since e85 is part gasoline it won't lower mileage as much as pure alcohol would. To run straight alcohol you need three times as much fuel as you would gasoline

 

Now that the subsidies are going away I doubt you will ever see it at that margin.

I base it on the price of premium so i can almost justify it.

 

Very true I always switch to 91 tune in winter because they cut it to E70 at the pumps. Definately will not be going back to the E85 tune with the E85 prices like they are.