Minnesota Focus Owners Club

For whatever reason I filled up with 91 octane on the stock yeller one. And it runs better, smoother and I think getting better gas milage at this point also. I'm thinking it's time for a timing belt maybe.

When using high Octane someone times the formula between a 91 or 93 octane could be the difference between a good idle and a great idle, either way. Depending on temperatures, the 91 could offer superior idle quality and part throttle response, where as the 93 might not as it's burn time is ever so slightly longer. Just saying.

If this is a standard Zetec, then this could be a sign of carbon buildup on the valves/pistons as well.

Looks like I'm getting another can of Seafoam after I use the half one now.

The can I had was a full one so I used that, big difference already so I picked up another can to use after it cools then the oil change.

There is absolutely no advantage(1) to using higher octane gasoline if the engine does not require it. In fact, you may experience a small loss of power, as the detonation does not occur at the precise time that the engine is set for. If your engine is designed for 87 octane gasoline, then it should run best with that.
(1) Except to BP, Shell, or whatever company you buy from!

oldoutboardjim wrote:There is absolutely no advantage(1) to using higher octane gasoline if the engine does not require it. In fact, you may experience a small loss of power, as the detonation does not occur at the precise time that the engine is set for. If your engine is designed for 87 octane gasoline, then it should run best with that.
(1) Except to BP, Shell, or whatever company you buy from!

Incorrect. The PCM looks at the knock sensor and keeps advancing timing until it starts to pre-ignite. With a higher octane level, the pcm is able to advance the timing farther than on lower octane levels thus allowing a more complete burn of the fuel in the combustion chamber. This will increase fuel economy and sometimes make the car run smoother. Cost wise from 87 to 91, it is not worth the extra 1-3mpg you will get. Just my .02

FocusMech.73155 wrote:Incorrect. The PCM looks at the knock sensor and keeps advancing timing until it starts to pre-ignite. With a higher octane level, the pcm is able to advance the timing farther than on lower octane levels thus allowing a more complete burn of the fuel in the combustion chamber. This will increase fuel economy and sometimes make the car run smoother. Cost wise from 87 to 91, it is not worth the extra 1-3mpg you will get. Just my .02

Oh contraire, Mr. Mechanic - unless this particular PCM is programmed to take advantage of higher octane (many aren't). For example, Chrysler minivan V6's will run on any old swill, and higher octane gas will only cause them to have heartburn. Another thing: If your "normally runs great, designed for 87 octane" engine seems to suddenly need higher octane, that's an indication of other issues.

2 cans of Seafoam in the vac and it runs much better.

oldoutboardjim wrote:

FocusMech.73155 wrote:Incorrect. The PCM looks at the knock sensor and keeps advancing timing until it starts to pre-ignite. With a higher octane level, the pcm is able to advance the timing farther than on lower octane levels thus allowing a more complete burn of the fuel in the combustion chamber. This will increase fuel economy and sometimes make the car run smoother. Cost wise from 87 to 91, it is not worth the extra 1-3mpg you will get. Just my .02

Oh contraire, Mr. Mechanic - unless this particular PCM is programmed to take advantage of higher octane (many aren't). For example, Chrysler minivan V6's will run on any old swill, and higher octane gas will only cause them to have heartburn. Another thing: If your "normally runs great, designed for 87 octane" engine seems to suddenly need higher octane, that's an indication of other issues.

Being you mention "unless", you simply don't know for fact. Whereas mech does.

The other part you don't see mentioned much, if at all, is how the 'adaptive learning' plays into ignition timing, among other things.


Basic fact is, yes better fuel can aid in more power / more timing in every single Ford EEC-V. How much will vary on many things and might not be noticed at all. ... take an old SBC/SBF, +1* can't be felt at all. Same thing with newer cars, but that doesn't mean it's not helping something somewhere (lowering PW's for instance).

iminhell wrote:How much will vary on many things and might not be noticed at all. ... take an old SBC/SBF, +1* can't be felt at all. Same thing with newer cars, but that doesn't mean it's not helping something somewhere

Yeah, it's helping something somewhere, alright: Helping BP's & Shell's bottom line. Helping to keep your wallet slim.

Yep the gas companies love it when you burn the non regular gas. Probably costs them pennies per gallon if that to give it just a little more octane.

BTW love the new handle Jim

Patalrob wrote:BTW love the new handle Jim

What the......? Oh well, if the shoe fits.

Patalrob wrote:Yep the gas companies love it when you burn the non regular gas. Probably costs them pennies per gallon if that to give it just a little more octane.

If you think about it, premium gas has always been 20-30 cents more per gallon. Hasn't changed much even though gas has quadrupled in the last 20 years. If it was going up by the same factor you would expect to see premium cost a dollar more per gallon than regular...

oldoutboardjim wrote:I wonder if the percentage of cars that require premium fuel is increasing or decreasing.

Require? I'd say decreasing simply due to the fact that cars are getting so much more sophisticated in the engine management.

Look at the 2012 Focus, it's 12:1 compression but will run happily all day on 87 octane unlike our old SVTs that kick and scream if you even try to run midgrade.

On the other hand cars that can take advantage of the higher octane fuels are increasing in numbers for the same reason, at the auto show lots of the spec sheets showed different horsepower ratings depending on the fuel you put in the tank.