What octane is everyone using?

[WAM]

For octane, most engines need what they need and more does nothing. Some engines use knock detection to optimize advance, so higher octane fuel serves a purpose -- up to a point.

Where does the FiST fall? Since the book says use 87, higher if towing, what does insisting on 93 get you? Talking stock here, not modded.

 

[jmrtsus]

For octane, most engines need what they need and more does nothing. Some engines use knock detection to optimize advance, so higher octane fuel serves a purpose -- up to a point.

Where does the FiST fall? Since the book says use 87, higher if towing, what does insisting on 93 get you? Talking stock here, not modded.

Your Factory ST supplement manual says basically 93 if you want the Horsepower you paid for........and my runs like crap on 87. There are places like the Upper Peninsula of Michigan where all I could find off the beaten road last summer was 87. Car runs on it, badly, tried it once....never again by choice.


Engine Specifications
Item Transversely mounted I4
cast aluminum cylinder block and cylinder heads
Configuration 79.0 mm bore x 81.4 mm stroke (3.11 in. x 3.20 in.) Bore x stroke
1597 cubic centimeters (97 cubic inches)Displacement
10.0:1 Compression ratio
197 hp @ 6350 RPM on 93 octane Horsepower
202 lb-ft @ 4200 RPM on 93 octane Torque

 

[WAM]

Your Factory ST supplement manual says basically 93 if you want the Horsepower you paid for........and my runs like crap on 87.

I can't find that in my 2016 ST Supplement. I'm only finding 87, plus premium suggested for trailer tow. Does yours actually say 93 somewhere? I'm still on my first tank of dealer purchased gas, so don't know what he put in. But I have no problem using 91 for daily use and blending to 93 for competition if I can tell a difference.

 

[jmrtsus]

I can't find that in my 2016 ST Supplement. I'm only finding 87, plus premium suggested for trailer tow. Does yours actually say 93 somewhere? I'm still on my first tank of dealer purchased gas, so don't know what he put in. But I have no problem using 91 for daily use and blending to 93 for competition if I can tell a difference.

Page 7 chart of Supplemental Manual. We have 93 non-ethanol here so only on the road does "FiFi" go off her diet!

 

[WAM]

Gotcha, thanks.

 

[Intuit]

Minus additional power, it'll run normally on 87 unless you get bad gas. Saying "it runs like crap" makes it sound like it's missing, backfiring, bad mileage, 22hp or other.

 

[neeqness]

On factory tune, it runs on 87 but imo not as smoothly as 91 or even 89. 89 has some problems too if I refill after putting 87. I prefer 93 though but unfortunately the highest octane commonly available in my area is 91.

After a very short experimental period I have decided to stick with 91 or better. It's not so bad for me since my last car required 91 so I'm used to it now.

Just for the record, although the manual recommends 87 it does say that premium fuel provides additional performance. Imo though 87 feels sluggish so I'll stick with 91 or 93 (when available)

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[jmrtsus]

Minus additional power, it'll run normally on 87 unless you get bad gas. Saying "it runs like crap" makes it sound like it's missing, backfiring, bad mileage, 22hp or other.

I think stumbling on full throttle acceleration like passing is running like crap. Milage also dropped off slightly but that was expected. Car did not run like "bad gas" (water), ran like the ECU was constantly trying to find a configuration (I think a retard/advance timing battle in the ECU) to operate correctly on hard acceleration. Who knows what was in the Holiday stations tank. I have never heard of them so I take it they are a regional company. They said on the pump 87 octane. That does not guarantee the tanker truck driver actually filled the tank with 87, nor that the terminal filled the truck correctly, for all I know it was E85 or such. There are go guarantees when humans are involved but I think that is unlikely. Maybe some member can clue me in about Holiday fuels. That is my experience with 87 octane.

Ford says the ST will run on it, they don't say how well.......they also hedge and tell you any "hard" driving to use 93, not much difference to the engine in a steep hill and towing a trailer. E. TN is hills and mountains and I know how my car performs on on these roads on 93 as most of my driving is here. The 87 is pure marketing, if they say 93 is required then Consumer Reports will rip them apart and the sticker will show a higher operating expense. The Fiesta owners manual covers ALL Fiestas but only the ST supplement gives the clue to loss of performance on lower than 93 octane in the ST engine.

 

[neeqness]

I strictly use top name brand fuels in my area (Chevron, 76, Shell)...and even among these brands I don't look for just the cheapest fuel I can find. I look for the "freshest" fuel, stations with a lot of traffic and quick turnover. If a station gets little traffic I tend to avoid it as old fuel can also cause sluggish conditions.

Even with that I find 87 octane sub-par for my purposes.

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[Intuit]

[MENTION=4988]neeqness[/MENTION] & [MENTION=2319]jmrtsus[/MENTION]
's advocate:
http://www.fiestastforum.com/forum/...everyone-using?p=152046&viewfull=1#post152046

Surprising results on 87 vs 93. I did wot pulls in third gear from 40-80 mph. Stock tune 87 octane stock airbox time to complete 6.5 seconds. 1/4 tank I the car. Test 2 93 octane MAP intake and stock tune. Result 6.5 seconds full tank. This was measured using a race logic, really slick unit. I did a 40-80 because it doesn't require a shift and takes driver out of the equation. My .02

Of course, doesn't exactly provide a lot of detail and is not a dynamometer, done on different days etc, etc.

Assuming 100% stock from intake to exhaust you're speaking from personal experiences so there's zero to be added to that; which is why I headed with "devil's advocate."

In ~12k I've only run 87 for a tank or two. Didn't notice any adverse affects but never fully floored it on 87. May give 87 another whirl just for curiosity.

 

[neeqness]

Why test 40 - 80? You could have done 15 or 20 - 50 in 3rd gear only for the same reasons...

But there are so many ways this test could be misleading that it's not funny. One reason being that no one drives only 40 - 80 mph. If you are going to test it, it should be as close to the actual use or the intended use as possible.

A better comparison would simply be driving it with a full tank of one in normal typical driving until nearly empty. Then filling with the other octane from the same station and driving that in your normal typical situation and compare the results. Besides adding testing instruments while doing this to help pinpoint and substantiate your findings, this is about as good as it gets.

The tank needs to be from full to empty each time or you can screw up the results. I.e.: 1/3 of a tank of 93 topped off with 87 octane brings the overall octane in the tank to 89...


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[Brickell FIST]

http://www.fiestastforum.com/forum/...-testing-stock-vs-stage-2?highlight=Racelogic

The reason 40-80 was to replicate a dyno pull or log used for the pro tuners to make adjustments. It goes from 2500-redline.

 

[Truth in Ruin]

I filled up with 95 E10. My car is stock. The car may have had more pep in it's step, but the biggest difference was the improved gas mileage.

 

[M-Sport fan]

I filled up with 95 E10. My car is stock. The car may have had more pep in it's step, but the biggest difference was the improved gas mileage.

Do you mean 93 E10, or can you actually get something 95 octane in your area?

 

[Truth in Ruin]

Do you mean 93 E10, or can you actually get something 95 octane in your area?

It's not a typo. 95 E10 at the pump.

 

[Capri to ST]

I can't see any reason to use less than 93 octane (91 where that's the max available) for a performance car like this. It gets decent gas mileage, and why buy a high-performance car but hinder it from reaching the maximum performance it's capable of to save a little on gas? I'm savings tons on gas even using 93 compared to my previous 11 mpg V-8.

That said, I do think Ford creates confusion by the way it deals with octane in the ST Supplemental Manual. On p.10 it clearly says 87 is recommended, with premium rec'd for severe duty such as trailer towing. On p.7, buried unhelpfully in a stack of engine specs, it shows the maximum hp and torque figures "on 93 octane." As some others have noted, "recommending" the lower octane fuel lets Ford make people think they will spend less on gas. To me, it would be a lot simpler and more honest if they would just recommend premium, and note that you can use regular but it will diminish performance.

 

[WAM]

Am I reading correctly that some people are blending in some E85 to get higher octanes while using the stock tune? It's always been my understanding that alcohol requires richer air/fuel ratios than gasoline, and adding alcohol to gasoline ought to lean out the engine unless you tune for it. Obviously it would depend on how much alcohol is mixed in, but I don't know what's considered a "safe" amount. And it's probably something people will argue about.

Some people who seem to know what they're doing say E25 is safe for a stock ST. My calculator says that's 1 gal E85 to 4 gal 91oct E10. Anyone buy that? Same calculator says the mix works out to about 93.8 octane assuming 105 for the E85.

 

[M-Sport fan]

Am I reading correctly that some people are blending in some E85 to get higher octanes while using the stock tune? It's always been my understanding that alcohol requires richer air/fuel ratios than gasoline, and adding alcohol to gasoline ought to lean out the engine unless you tune for it. Obviously it would depend on how much alcohol is mixed in, but I don't know what's considered a "safe" amount. And it's probably something people will argue about.

Some people who seem to know what they're doing say E25 is safe for a stock ST. My calculator says that's 1 gal E85 to 4 gal 91oct E10. Anyone buy that? Same calculator says the mix works out to about 93.8 octane assuming 105 for the E85.

The sensor driven, O.A.R. (Octane Adjust Ratio) program in our ECU may actually be sensitive enough to be able to compensate for that ethanol 'leaning effect', especially in conjunction with direct injection.

Maybe someone with much more knowledge/experience with this system can chime in to either confirm, or refute this idea.

I have been using an E20-E25/93 blend on a factory tune, with no noticeable ill effects so far, but admittedly, I am not data logging corrections currently.
I will continue to use this blend when I install the 93 E10 Stratified Flash tune, just to have an extra 'octane safety margin' on that tune, especially in the summer heat.

 

[Truth in Ruin]

The sensor driven, O.A.R. (Octane Adjust Ratio) program in our ECU may actually be sensitive enough to be able to compensate for that ethanol 'leaning effect', especially in conjunction with direct injection.

Maybe someone with much more knowledge/experience with this system can chime in to either confirm, or refute this idea.

I have been using an E20-E25/93 blend on a factory tune, with no noticeable ill effects so far, but admittedly, I am not data logging corrections currently.
I will continue to use this blend when I install the 93 E10 Stratified Flash tune, just to have an extra 'octane safety margin' on that tune, especially in the summer heat.

As far as performance, how noticeable is the E20/25 mix on the stock tune?

 

[M-Sport fan]

As far as performance, how noticeable is the E20/25 mix on the stock tune?

According to razorlab's posts, it IS an actual, measurable amount, and it feels like a discernible difference, but then I am still not pushing this car to the max yet, even accelerating on an empty, LEO-free road (it only has ~3K miles on it now).
http://www.fiestastforum.com/forum/threads/10046-Second-FiST-2016-Fiesta-ST

Still, even at lesser throttle angles, it does feel more potent (can't wait to get the cp-e IC in, and Strat Flash tune loaded).