anyone using premium gas ?

[tmnCA]

Originally Posted by BetaDnB

Here's what it says on page 351 RE fuel ethanol/E85

During the summer season, fuel ethanol may contain a maximum of 85%
denatured ethanol (Ed85) and 15% unleaded gasoline. The fuel ethanol
has a higher octane rating than unleaded regular or premium gasoline
and this allows the design of engines with greater efficiency and power.

This basically says higher octane = greater efficiency and power.

Actually, the above quote says that this fuel "allows the design of" engines with more power etc. It does not say if you put this fuel in your car that you will get more more or efficiency.

[Dgc333]

Originally Posted by BetaDnB

Here's what it says on page 351 RE fuel ethanol/E85

During the summer season, fuel ethanol may contain a maximum of 85%
denatured ethanol (Ed85) and 15% unleaded gasoline. The fuel ethanol
has a higher octane rating than unleaded regular or premium gasoline
and this allows the design of engines with greater efficiency and power.

This basically says higher octane = greater efficiency and power.

Pg 351 is talking about flex fuel vehicles which i don't believe the 12 Focus is yet (mine isn't) so you can't even use E85. Typically flex fuel vehicles get about 25% less mileage compared to running it on gasoline and make less power too.

Yes, an engine designed to run on just E85 can have very high compression allowing it to make more power but because E85 has less energy content than gasoline will always use more. But a flex fuel vehicle is designed to run on both gasoline and E85 so it can't be designed to take advantage of the 100+ octane rating of E85, still needs to run on 87 octane gasoline.

So, "higher octane = greater efficiency and power." is wrong when it comes to the Focus.

My comment was in response to the first paragraph under "Octane recommendations" on pg 354. Where the sentence; "Premium fuel will provide improved performance." You can't take that out of context from the rest of the paragraph.

[BetaDnB]

Originally Posted by Dgc333

My comment was in response to the first paragraph under "Octane recommendations" on pg 354. Where the sentence; "Premium fuel will provide improved performance." You can't take that out of context from the rest of the paragraph.

I incorrectly read what I posted. I agree with you about page 354, but beware, there are some who seem to take that sentence way out of context and make it something it's not.

[Dgc333]

Originally Posted by zak404

Running premium fuel allows the engine computer to advance the timing thus resulting in more power on the lower end torque curve, the burn time for higher octane fuel is also longer resulting in more power.
It would be interesting to see some dyno tests done with regular fuel and premium fuel.
Any of you that used to race will remember what quicker advance curves did for cars.

Adding advance does not necessarily mean more power. To get max power and efficiency maximum cylinder pressure needs to occur approximately 20 degrees after TDC. To much timing will hurt power just as much as too little.

Back when cars had distributors and springs/weights/vacuum controlled the advance curve the engineers didn't have the CAD tools to design and model engine designs that are available today. Quite often you couldn't establish the ideal advance curve because of poor combustion chamber design and inconsistent manufacturing so they established safe limits. This allowed the enthusiast to tune for their needs and make a significant improvement.

Today designs are very well optimized before the first piece of metal is machined and there is much less room for improvement.

A muscle car era bug block mopar needs upwards of 40 degrees of advance to make max power. The current generation Hemi, LS or Mod Motor makes max power with less than 30 degrees of advance and runs to much higher rpms.

[zak404]

So you're saying premium gas won't advance the spark curve for better low end power?

[kbass24emtp]

My wife has tried 87 and 89 and get better milage with the 89. She refuses to try premuim.

[redav]

Originally Posted by BowerR64

If lower grade fuel causes knock and retard timing how can it be better to use that fuel?

There is much more to fuel than octane. Different brands use different additives, such as detergents, lubricants, surface protectants, etc. 'Top Tier' brands use much more cleaning agents than required by law, and they will keep the engine running better, longer.

Thus, using a good (e.g., 'Top Tier') 87 octane fuel is better than using a crappy (e.g., oxidized, off-season, no-additives) 93 octane.

You are incorrect in your statement about causing knock. The Focus' engine does not knock when using 87 octane because it adjusts the timing. Of course, it is not getting as much power as it could get with a higher octane fuel, but that is of small importance compared to the cleanliness and life of the engine.

[Dgc333]

Originally Posted by zak404

So you're saying premium gas won't advance the spark curve for better low end power?

No it won't. It might keep it from being retarded but it won't advance it beyond what the engine was tuned for. Plus an engine needs less timing advance at low RPMs than at high RPMs. The engine needs the most timing advance at light load cruising when the throttle is barely open. Under this condition the cylinder does not fill with air/fuel efficiently so the spark has to happen sooner to ensure max cylinder pressure occurs at the approx 20 degrees ATDC i mentioned previously.

In the old days distributors had mechanical advance that was strickly rpm dependent, more rpms, more advance. They also had vacuum advance that added more timing in high manifold vacuum conditions such as light load cruising.

[tvfocus]

I guess most people are not aware that all gas (in the area you live) is created equal. This is because for each area of the country their is only one refinery making the gas. This is especially true during the Summer, due to the EPA requiring at least 18 different formulations for at least 18 different parts of the country. Twice a year all refineries shut down for about 2 weeks so they can reformulate per EPA rules.

Here in Florida almost all of our gas comes from one refinery in the Gulf coast. Now the only difference between brands is that when the gas is moved from the refinery to storage tanks Shell, Mobil or whatever brand can then add additional additives if they want to. Otherwise all the gas (regular, Plus and Premium) has the same cleaning additives that the EPA requires. Also the Refinery only makes Regular and Premium. Plus is made by just blending Regular with Premium either at the retailers storage tanks or at the gas station.

[flingwing1969]

Originally Posted by tvfocus

I guess most people are not aware that all gas (in the area you live) is created equal. This is because for each area of the country their is only one refinery making the gas. This is especially true during the Summer, due to the EPA requiring at least 18 different formulations for at least 18 different parts of the country. Twice a year all refineries shut down for about 2 weeks so they can reformulate per EPA rules.

Here in Florida almost all of our gas comes from one refinery in the Gulf coast. Now the only difference between brands is that when the gas is moved from the refinery to storage tanks Shell, Mobil or whatever brand can then add additional additives if they want to. Otherwise all the gas (regular, Plus and Premium) has the same cleaning additives that the EPA requires. Also the Refinery only makes Regular and Premium. Plus is made by just blending Regular with Premium either at the retailers storage tanks or at the gas station.

We have 22 refineries here in California. I ran one tank of premium through, and, although I thought is smoothed out my tranny's slight start-from-stop shudder, I didn't notice a difference in anything else - but I don't flog it anyway. I'm back to regular and I don't even notice any difference in the shifting.