Focus Fanatics Forum banner

1 - 20 of 39 Posts

·
Registered
Joined
·
343 Posts
Discussion Starter #1
Could be fixed by running 93 octane???

The 2012 ford focus has a 12:1 compression ratio, which is rather high for a non performance road car.

So if 87 octane is the lowest rated octane safe for use, though it still may combust to early or combust inefficiently (due to 12:1 ratio).



What octane do you use?
Have you had engine bogging?
And what's your mpg with 87 and then with 93?

I would test this out with a se 5spd but i have to sell my truck so i can finance the focus :) then i shall test this if no one has yet!
 

·
Registered
Joined
·
343 Posts
Discussion Starter #2
Gasoline contains many components and two are heptane and octane.
Heptane contains a 7 carbon chain and octane contains a 8 carbon chain.
Higher octane rating means more octane less heptane.
Heptane combusts with less pressure while octane requires more.

so along with requiring more pressure to combust higher octane gas conatins more energy due to more carbon in the chain.

an engine designed to utilize higher octane will gain more performance and gas mileage with use of higher octane fuel.
 

·
Registered
Joined
·
266 Posts
Modern engines in automobiles have a knock sensor that detects the predetonation of fuel in the combustion camber. The engine compensates by retarding the spark until a knock is not detected. I should note higher octane fuels have the same amount of energy as lower octane fuels. The engine may have a better efficiency (Converting chemical energy into mechanical energy) using a higher octane gas. This could result in a more horsepower (I highly doubt it is anything noticeable 1-2 BHP? ) and maybe some improved throttle response.
 

·
Registered
Joined
·
343 Posts
Discussion Starter #7
What happens when you run to low of octane in a vehicle that requires 91...
Besides knocking it will bog down and have low gas mileage.

The manual states that 87 is the lowest possible and higher will yield better performance.

I dont know any other vehicle that has a 12:1 ratio that dosnt require 91 octane. The gdi makes lower possible but still. Seems to be a problem
 

·
Registered
Joined
·
4,328 Posts
I dont know any other vehicle that has a 12:1 ratio that dosnt require 91 octane.
Direct injection lets you get away with a lower octane - it can't pre-ignite if it's not in the combustion chamber yet!
 

·
Registered
Joined
·
4,328 Posts
Thats why I said the gdi makes it possible
My bad... [:I]

And this, kids, is why you should get more than 4 hours of sleep after drinking on a Thursday night.
 

·
Sonic Crew #04
Joined
·
7,513 Posts
Could be fixed by running 93 octane???

The 2012 ford focus has a 12:1 compression ratio, which is rather high for a non performance road car.

So if 87 octane is the lowest rated octane safe for use, though it still may combust to early or combust inefficiently (due to 12:1 ratio).
What octane do you use?
Have you had engine bogging?
And what's your mpg with 87 and then with 93?
It may help slightly with the engine bog, but there are a lot of other factors with that. As for MPG there is debate but from my testing with no ethanol gas

91 octane 29.6MPG(5 tanks)
89 octane 30.2MPG(3 tanks)
87 octane 29.4MPG(6 tanks)

Less than 1 mpg difference between octanes
 

·
Registered
Joined
·
3,673 Posts
Could be fixed by running 93 octane???
There has been a fair amount of empirical evidence to suggest that there may be a small amount of knock (in certain conditions) when using 87.

If that is a concern, why not use 89?

If a 911 turbo or Nissan GT-R can run well on 91 (the max in California), why does a Focus need 93?
 

·
Registered
Joined
·
4,328 Posts
If a 911 turbo or Nissan GT-R can run well on 91 (the max in California), why does a Focus need 93?
Touché...

I think a lot of the pro-premium empirical data doesn't take into account the placebo effect nor the break-in period. Now that my car is broken in, I found out I get about 36 mpg no matter which octane I use. For hot summer months, I might switch to 89. Otherwise, I think it's probably unnecessary.

But there's a debate for that on another thread. Back to engine bog...
 

·
Registered
Joined
·
266 Posts
What happens when you run to low of octane in a vehicle that requires 91...
Besides knocking it will bog down and have low gas mileage.

The manual states that 87 is the lowest possible and higher will yield better performance.

I dont know any other vehicle that has a 12:1 ratio that dosnt require 91 octane. The gdi makes lower possible but still. Seems to be a problem
F350 Powerstroke diesel [hihi] but seriously you are right I am not sure of any other gasoline engine with high compression that doesn't require high octane. Though I do remember reading somewhere that the government mandates at least using 87 octane on all vehicles. I don't know if this is a legitimate statement or not.

It may help slightly with the engine bog, but there are a lot of other factors with that. As for MPG there is debate but from my testing with no ethanol gas

91 octane 29.6MPG(5 tanks)
89 octane 30.2MPG(3 tanks)
87 octane 29.4MPG(6 tanks)

Less than 1 mpg difference between octanes
That is a good note. Try getting gasoline with the least amount of ethanol in it. There will be more energy in the gas if you get "pure" gasoline. So there is more energy initially can be converted to mechanical.
 

·
Registered
Joined
·
4,328 Posts
That is a good note. Try getting gasoline with the least amount of ethanol in it. There will be more energy in the gas if you get "pure" gasoline. So there is more energy initially can be converted to mechanical.
True. Also, it will help with narrowing down dissimilarities in octanes. If you use ethanol-free gas for fuel testing, it is what it is. With ethanol, you don't actually know if you have 8% premium or 10% ethanol or how that works. (At least, my gas station never told me anything more than "up to 10%")
 

·
Registered
Joined
·
100 Posts
Personally, I've got the bog and low mileage "problem", which I think is just because the car likely has a lighter flywheel. My other 2 stick vehicles are much easier to get moving from a standstill. I've also been using 93 octane, but so far, my first few tanks have been:
tank 1 - 21.7mpg
Tank 2 - 23.7mpg (took it easy, mostly hwy, got full petals on eco, except shifting 3/5
Tank 3 - 18.7 :( mostly around town, mastered the full petals across the board.

The odd thing is that I've been getting full petals from the eco-meter, so it's not like I'm driving it hard. I've been taking it easy while I'm breaking it in, I'm just hoping that once it's broken in, it improves. I traded in my Fiesta because I needed a little more room and they both had the same window sticker mileage, so far, I'm getting on average 10mpg less than each fillup with my Fiesta for its first 3 tanks. :(
 

·
Registered
Joined
·
4,328 Posts
...so far, I'm getting on average 10mpg less than each fillup with my Fiesta for its first 3 tanks. :(
Don't worry, it should get better after it breaks in. My car was doing poorly when I first bought it and I was made fun of for buying a new car that only got 30mpg. Depending if I drive mostly city or highway it's between 34 and 41 on average.
 

·
Rubber Side Down
Joined
·
2,415 Posts
Definitely not a fix for bogging. I only run E0 91 octane.
Posted via FF Mobile
 

·
Registered
Joined
·
123 Posts
I found a gas station that actually has ethanol-free 91, I'm going to try that for my next tank. I'm guessing that the lack of ethanol would have a bigger effect than the 91 octane.
 
1 - 20 of 39 Posts
Top