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Old 10-11-2011, 01:44 AM   #1
PoP_91
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Default 87 vs 91/93 octane fuel

Hey FFC,

I have been wanting to ask this for a while now but keep forgetting to ask.

I remember being told somewhere that the stock 3.5L sport engine was designed to work optimally with regular fuel (87 octane). And that using a higher octane fuel could actually DAMAGE the engine?

is there any truth to this?

Thanks!
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Old 10-11-2011, 02:45 AM   #2
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Default Re: 87 vs 91/93 octane fuel

The engine is designed to run with 87 octane. Moving to a higher Octane like 91 or even 93 won't *damage* the motor, but it may not run as efficiently so you could lose power and your mileage may worsen.

I use Shell 91 (ethanol free) in mine and have no issues.
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Old 10-11-2011, 02:52 AM   #3
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Default Re: 87 vs 91/93 octane fuel

If you want to run higher octane and have all the benefits you should get a tune.
I tried 91 for a while. Didn't have any issues, but didn't see any benefit either.
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Old 10-11-2011, 07:14 AM   #4
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Default Re: 87 vs 91/93 octane fuel

Yeah there's really no reason to run anything higher than 87 unless you have a tune.
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Old 10-11-2011, 07:19 AM   #5
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Default Re: 87 vs 91/93 octane fuel

[quote author=acedeuce802 link=topic=199631.msg4128759#msg4128759 date=1318331675]
Yeah there's really no reason to run anything higher than 87 unless you have a tune.
[/quote]

Except in the winter. There are a lot of additives in the "winter" gas that dont help gas mileage any. Run 91 or 93 in the winter and you will actually notice a difference from running 87 in the winter. (Pending you live in the northnern half)
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Old 10-11-2011, 07:24 AM   #6
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Default Re: 87 vs 91/93 octane fuel

Hmm interesting. I'll have to try that out!
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Old 10-11-2011, 10:10 AM   #7
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Default Re: 87 vs 91/93 octane fuel

Hi PoP. Assuming you use a high quality/name brand fuel and do not have an aftermarket "tune", 87 octane is all you need (as per Ford). As Canadian mentioned, you will see no benefit by using a mid-grade or premium fuel. They will not "damage" the engine, but provide no benefit, can lead to a loss of efficiency and cost more. :shock:

Concerning "winter" fuels: In those areas of the country that already have fuel containing 10% ethanol, there is essentially no such thing as a "winter" fuel anymore. Fuels containing ethanol are already "winterized". Most of us (in the U.S. anyway) now drive with the same basic fuel formulation all year long and a switch to premium is not needed. While there are sometimes minor differences, they are inconsequential when it comes to performance and efficiency.

Short story? The old "Winter" fuel formulations contained an oxygenating additive. That was what made them "winter" fuels. In most cases, that oxygenating chemical was "MTBE". However, those same geniuses who mandated oxygenated fuels later discovered that MTBE leeches into our groundwater, severely polluting it, so MTBE is now out. Now the primary oxygenation factor is ethanol. And as we all know, most pumps (but not all) in most areas of the country now have 10% ethanol in the fuel all year long. That essentially means that most of us have the same oxygenated fuel formulation for 365 days of the year. So if you are already using 87 octane fuel with 10% ethanol, there is no need to change to a higher octane fuel in the "winter". You will only be lightening your wallet.

Of course, without getting into a chemistry dissertation (which I am not qualified to do anyway), the above is all simply a basic explanation. The drop in performance and efficiency we see in the winter is mainly due to the colder temperatures and other environmental or driving factors, not the fuel formulation. So the bottom line is that as Ford clearly informs us as owners, 87 octane is all our vehicles need for all four seasons of the year.

Hope this information helps.

Good luck.
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Old 10-12-2011, 03:50 AM   #8
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Default Re: 87 vs 91/93 octane fuel

Seasonal blended fuel does indeed still exist, even in California.

The primary reason for seasonal blending is two fold. In the winter, fuel that vaporizes easy is needed to start engines in cold weather. In the summer, such fuel vaporizes too easily and causes problems with vapor emissions and driveability as well as cutting fuel economy.

The index of this vaporization is RVP or Reed Vapor Pressure (or is it Reid, I forget). High RVP is needed in winter, and low RVP is needed in summer. Seasonal blending is always changing. My refinery friends tell me it is as often as every six weeks.

Another application of low RVP is piston aircraft engines. Altitude changes play hell on fuel vaporization. To enable starting in cold weather, airplanes use fuel heaters. From past experience I can tell you that when I ran aviation fuel in some of my old cars, that unless I kept about 20% to 25% pump gas, the engine would not start on cold mornings. Unfortunately, that was a dead giveaway that I had doctored fuel at the drag strip.

California may have stricter fuel requirements, including the need for cleaner fuels, but adding light ends such a butane in winter to raise the RVP is still done by necessity. Until cars have aircraft style fuel heaters, it is a necessity.
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Old 10-12-2011, 10:15 AM   #9
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Default Re: 87 vs 91/93 octane fuel

[quote author=Big Jim link=topic=199631.msg4129359#msg4129359 date=1318405858]
Seasonal blended fuel does indeed still exist, even in California.

The primary reason for seasonal blending is two fold. In the winter, fuel that vaporizes easy is needed to start engines in cold weather. In the summer, such fuel vaporizes too easily and causes problems with vapor emissions and driveability as well as cutting fuel economy.

The index of this vaporization is RVP or Reed Vapor Pressure (or is it Reid, I forget). High RVP is needed in winter, and low RVP is needed in summer. Seasonal blending is always changing. My refinery friends tell me it is as often as every six weeks.

Another application of low RVP is piston aircraft engines. Altitude changes play hell on fuel vaporization. To enable starting in cold weather, airplanes use fuel heaters. From past experience I can tell you that when I ran aviation fuel in some of my old cars, that unless I kept about 20% to 25% pump gas, the engine would not start on cold mornings. Unfortunately, that was a dead giveaway that I had doctored fuel at the drag strip.

California may have stricter fuel requirements, including the need for cleaner fuels, but adding light ends such a butane in winter to raise the RVP is still done by necessity. Until cars have aircraft style fuel heaters, it is a necessity.
[/quote]

Hi Big Jim. Yes, you are correct that seasonal blends do exist in some areas, that is why I qualified all of my statements with "most of us" (meaning not all), "essentially", "effectively" etc., to make it clear I was not making a blanket statement for all areas of the country. And yes, California is certainly an entirely different subject when it comes to regulations concerning emissions, fuel etc..

While I went into too much side detail on the winter gas, my basic intent was only to make it clear that contrary to what some people may believe, Fusion/MKZ/Milan owners do not need to use 91-93 octane fuel in the winter. As per Ford, our cars are designed to run on 87 octane fuel nd using a higher octane blend on a factory tuned car will only lighten our wallets.

Sorry for the information detour on the winter gas formulations.

Good luck.
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Old 10-12-2011, 10:29 AM   #10
Big Jim
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Default Re: 87 vs 91/93 octane fuel

[quote author=bbf2530 link=topic=199631.msg4129429#msg4129429 date=1318428919]
[quote author=Big Jim link=topic=199631.msg4129359#msg4129359 date=1318405858]
Seasonal blended fuel does indeed still exist, even in California.

The primary reason for seasonal blending is two fold. In the winter, fuel that vaporizes easy is needed to start engines in cold weather. In the summer, such fuel vaporizes too easily and causes problems with vapor emissions and driveability as well as cutting fuel economy.

The index of this vaporization is RVP or Reed Vapor Pressure (or is it Reid, I forget). High RVP is needed in winter, and low RVP is needed in summer. Seasonal blending is always changing. My refinery friends tell me it is as often as every six weeks.

Another application of low RVP is piston aircraft engines. Altitude changes play hell on fuel vaporization. To enable starting in cold weather, airplanes use fuel heaters. From past experience I can tell you that when I ran aviation fuel in some of my old cars, that unless I kept about 20% to 25% pump gas, the engine would not start on cold mornings. Unfortunately, that was a dead giveaway that I had doctored fuel at the drag strip.

California may have stricter fuel requirements, including the need for cleaner fuels, but adding light ends such a butane in winter to raise the RVP is still done by necessity. Until cars have aircraft style fuel heaters, it is a necessity.
[/quote]

Hi Big Jim. Yes, you are correct that seasonal blends do exist in some areas, that is why I qualified all of my statements with "most of us" (meaning not all), "essentially", "effectively" etc., to make it clear I was not making a blanket statement for all areas of the country. And yes, California is certainly an entirely different subject when it comes to regulations concerning emissions, fuel etc..

While I went into too much side detail on the winter gas, my basic intent was only to make it clear that contrary to what some people may believe, Fusion/MKZ/Milan owners do not need to use 91-93 octane fuel in the winter. As per Ford, our cars are designed to run on 87 octane fuel nd using a higher octane blend on a factory tuned car will only lighten our wallets.

Sorry for the information detour on the winter gas formulations.

Good luck.
[/quote]

I agree with the fact that octane ratings above 87 are not needed for most Ford products. There are a few that should run higher octane fuel (like the Taurus SHO).

Ford published a TSB back in the 90's on the subject. I have no idea if it is still appropriate information. The gist of the bulletin was that the stuff blended into the fuel to raise octane also tended to aggravate cold start and light throttle stumble. This may be alleviated today by different fuel blending techniques or improved engine tuning. I mention this in support of your observation that higher octane fuel does nothing if it is not needed. I also mention it in support that that there is something historically that supports that Ford, at least back then, took the position that high octane may actually have a negative effect.
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