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Confusion aboout fuel recommendation

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Old 05-03-2014, 07:50 AM   #21
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That's very interesting & good to know. Where did you get this information?
I used to work for a Harley dealer and I asked my service manager the same question about my bike. It's more critical with an air cooled engine of course, but heat is heat and it's an enemy.
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Old 05-03-2014, 09:37 AM   #22
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The '13 manual states "recommended fuel--87 octane" (page 160-ish); No mention of 91/93. 8 hp isn't noticeable by the seat of your pants, but, I guess if you are drag racing you will want every horse you can get. I run 91/93 because of the compression ratio. I know its kinda old school considering the computer has the ability to sense knock. I'm just not that trusting.
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Old 05-03-2014, 02:34 PM   #23
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The '13 manual states "recommended fuel--87 octane" (page 160-ish); No mention of 91/93. 8 hp isn't noticeable by the seat of your pants, but, I guess if you are drag racing you will want every horse you can get. I run 91/93 because of the compression ratio. I know its kinda old school considering the computer has the ability to sense knock. I'm just not that trusting.
oops, i lied. It's actually 18hp, according to Ford. Ford claims 402hp at the crank with 87, and 420hp with premium. I did have a source for this, but can't find it now. It was from a source like Car and Driver
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Old 05-03-2014, 03:08 PM   #24
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And of course the Mustang page on the Ford website, under specs, and then the engine tab, states HP and TQ figures are with Premium fuel, except the V-6.
Then lower on the page it has recommended fuel, V-6 Unleaded Regular, GT Unleaded Premium, and the GT500 also Unleaded Premium.
So which is right the owners manual, or the Website, maybe the Ford rep could check on this for us, for me I'll stick with one less fancy coffee a week and use Premium.
I think more important is to always use a top tier fuel, I like Chevron, as Techron is the one additive most all experts will agree works, and does no harm.
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Old 05-03-2014, 04:09 PM   #25
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And of course the Mustang page on the Ford website, under specs, and then the engine tab, states HP and TQ figures are with Premium fuel, except the V-6.
Then lower on the page it has recommended fuel, V-6 Unleaded Regular, GT Unleaded Premium, and the GT500 also Unleaded Premium.
So which is right the owners manual, or the Website, maybe the Ford rep could check on this for us, for me I'll stick with one less fancy coffee a week and use Premium.
I think more important is to always use a top tier fuel, I like Chevron, as Techron is the one additive most all experts will agree works, and does no harm.
They are both technically right. It's recommended to use 87 at a minimum, but if you want full performance, you need premium. If someone isn't worried about performance and just wants fuel savings, then go with 87. If you're a car fanatic, like most of us, you will want premium for the performance.

One thing to remember though. Like all systems that fluctuate timing based on A/F ratio, it can take an entire tank of fuel, or longer, to completely adjust. At least, that's how it was a few years ago. It might be a little better, but regardless, the change is not instant.
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Old 05-05-2014, 11:07 AM   #26
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I've made 439 fwhp on 91 octane fuel, with a mild Ford racing tune that asks for 91 minimum, no other power mods. I ran 87 on the car when it was stock tune to try it and it was no problem. The car has so much power for around town, it wasn't really detectable. I think you'd want a little more octane headroom if you were planning on racing the car; it does soften up a tiny bit when it gets warm or the DA goes up, like all n/a engines.

Just buy quality gas, whatever you choose. Off brands are ofen blended and won't necessarily meet the rating. 87 ends up being more like 85, etc. This is an 11.1 compression engine so, quality fuel is needed.
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Old 05-07-2014, 07:06 AM   #27
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I have opted for 93 octane non-ethanol fuel for mine. It's the non-ethanol fuel that is available at the "GOGAS" chain stores in our state. I figure that it's worth the extra coin to stay away from ethanol and if the octane gives some extra HP, so much the better.

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Old 05-07-2014, 08:00 AM   #28
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Just buy quality gas, whatever you choose. Off brands are ofen blended and won't necessarily meet the rating. 87 ends up being more like 85, etc. This is an 11.1 compression engine so, quality fuel is needed.
Well said, and I fully agree that quality gas is important. However, those who are pinching pennies and not putting 91/93 in their tank will surely go to the cheapest station around and fill up with 87.
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Old 05-09-2014, 05:42 PM   #29
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I fill up once a week. I figure the 93 costs me $3.20 a tank over 87. I understand that the 87 actually burns hotter. More heat=more wear and tear. For me, it's worth $12.80 a month.
I'm pretty certain that it doesn't burn hotter/cooler, it just determines if it is resistant to knock/detonation

https://mn.gov/commerce/weights-and-...ctaneFacts.pdf

It costs more because it has extra refining steps. These cars have knock sensors that advance/retard timing based on if knock is detected. If you can find any credible source of information about 87 or 93 burning hotter/colder I'd like to see it. Everything I found said it burns at the same temp, it's just a difference of how resistant it is to heat sources(detonation). burning hotter/colder slower/faster are laymans terms for it. It isn't what is actually going on, if they are both achieving combustion with the same amount of fuel it's an equal heat generation(they have the same BTU).

http://www.consumerenergycenter.org/...s_premium.html



also to someone else, My dealership filled my car up with 91 (highest available here) I know because I was there when the sales person filled it up.
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Old 05-09-2014, 06:23 PM   #30
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I'm pretty certain that it doesn't burn hotter/cooler, it just determines if it is resistant to knock/detonation

https://mn.gov/commerce/weights-and-...ctaneFacts.pdf

It costs more because it has extra refining steps. These cars have knock sensors that advance/retard timing based on if knock is detected. If you can find any credible source of information about 87 or 93 burning hotter/colder I'd like to see it. Everything I found said it burns at the same temp, it's just a difference of how resistant it is to heat sources(detonation). burning hotter/colder slower/faster are laymans terms for it. It isn't what is actually going on, if they are both achieving combustion with the same amount of fuel it's an equal heat generation(they have the same BTU).

http://www.consumerenergycenter.org/...s_premium.html



also to someone else, My dealership filled my car up with 91 (highest available here) I know because I was there when the sales person filled it up.
Hmmmm, according to the PDF you linked, under Octane facts it states "High octane gasoline burns slower than low octane gasoline. The slow burn prevents engine knock when cylinder pressures are high.".
So by the evidence you presented it is not just a layman's term but a fact.
But should I trust anything from Minnesota's government, or any branch of the government for that matter.
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Old 05-09-2014, 08:27 PM   #31
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It costs more because it has extra refining steps.
no, not really. octane rating of gasoline is about the additive package. the base fuel is the same. a fuel's octane rating is an indicator of its ability to resist autoignition, meaning how much heat and pressure it can undergo without lighting off until the spark plug fires. additives drastically alter the base gasoline's anti-knock properties; one of the reasons tetraethyl lead used to be a popular additive to gas was because even a tiny amoung boosted the fuel's octane rating substantially. Of course, it had the nasty property of fouling the air we all breathe with lead...

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I'm pretty certain that it doesn't burn hotter/cooler, it just determines if it is resistant to knock/detonation
this is accurate. the burn rate/temperature of gasoline is pretty much consistent across all grades.
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Old 05-10-2014, 04:46 PM   #32
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additives for anti-detonation - low octane with spark advance on a high compression engine means the fuel will ignite / detonate sooner than it should causing pinging or blasting holes in your pistons is how I understand it. Old school aircraft engines like a PW R2800 (2800 cubc inches with 18 cylinders) were built for 150 octane av gas (if I remember correctly) which has not been made for 40 / 50 years. At high power settings they also used ADI (anti detonation injection) fluid (water / methonal) as well to control detonation. These engines are now stuck with 100/ 130 octane and can no longer pull full rated power.
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Old 05-11-2014, 12:00 PM   #33
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You can't compare avgas and mogas ratings. They are rated using different methods and have completely different purposes in rating. Avgas typically has two ratings. The low one is "aviation lean" which is your cruise performance and "aviation rich", which produces max power on the same fuel.

The PW2800 was quite capable of making 2800 horses, rated, in later versions, on 115 octane fuel (actually 115/145). The best at this were the Chermans. High octane avgas got more scarce as the war went on and they really had to figure out how to make rated power on what was, essentially, 87 octane fuel. People don't run these old birds as hard today because the engines are 70 years old, parts are hard to get and $$$$ and there's little available 100/130 or 115/145 (leaded) avgas any more. Nowadays, 100LL is the highest performance leaded avgas commonly available and it hasn't got enough lead to keep these old engines happy in stock form.

Main differences with avgas over mogas is the much higher vapour lock resistance. Vapour lock is easy to get at altitude and that's it, engine shut down and probable crash landing so, pretty serious stuff.
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Old 05-13-2014, 03:38 PM   #34
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My manual specifically recommends high octane.
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Old 06-29-2014, 09:49 AM   #35
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When I bought my car, I went with the salesperson so that he could give me a full tank of fuel. I asked if he was going to use 93 octane or 87. He told me if he pumped 93 octane, and turned in that invoice, he would be either reprimanded or fired by his boss. This is coming from a Ford dealer on a new 2014 Mustang GT. I typically mix my gas at half tank. Once using 87 and next time 93 octane. I have tried running both separately, and I felt no difference between them at all, even at low rpms.
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Old 06-29-2014, 06:07 PM   #36
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When I bought my car, I went with the salesperson so that he could give me a full tank of fuel. I asked if he was going to use 93 octane or 87. He told me if he pumped 93 octane, and turned in that invoice, he would be either reprimanded or fired by his boss. This is coming from a Ford dealer on a new 2014 Mustang GT. I typically mix my gas at half tank. Once using 87 and next time 93 octane. I have tried running both separately, and I felt no difference between them at all, even at low rpms.
93 octane on the stock Ford tune is useless. The PCM's ECU is programmed at most to exploit 91 octane and nothing more. The PCM does not store any timing advance values for anything above 91 octane.
The reason being is 93 octane is not available in most places with 91octane being the best fuel you can buy at the pump.

But since you mix 87 octane and 93 octane half and half, you are hitting around 89-90 octane in the end. So you are close to the max PCM tuning programming, assuming you are still using the stock Ford tune.

To be very honest, you will not feel the difference between 87octane and 91octane on the stock tune. The most crank torque you will get is 390 ft-lbf, with maybe only 385 ft-lbf on 87 octane. 5 ft-lbf crank torque gain is a very small, it is more like 3ft-lbf gain at the wheels.
The only way you will feel more power is if you get an aftermarket tune.
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Old 07-10-2014, 12:20 PM   #37
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I run 87 in my 2014 5.0 most of the time. Because, most of the time I am just commuting back and forth to work and honestly wouldn't miss 50 hp! Even with 87 octane, the car is stupid fast for a 100% stock-off-the-shelf Mustang.
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Old 07-12-2014, 10:45 AM   #38
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When I bought my car, I went with the salesperson so that he could give me a full tank of fuel. I asked if he was going to use 93 octane or 87. He told me if he pumped 93 octane, and turned in that invoice, he would be either reprimanded or fired by his boss. This is coming from a Ford dealer on a new 2014 Mustang GT. I typically mix my gas at half tank. Once using 87 and next time 93 octane. I have tried running both separately, and I felt no difference between them at all, even at low rpms.
Same here. I asked for 91, and my salesman said he was only authorized to do that for Shelby's and one other vehicle that wasn't mine.

I fill up early, alternating between 89 and 93, as 91 is often unavailable as pumps will be 87, 89, then jump to 93. Some have 91.

Last edited by GTC; 07-12-2014 at 10:48 AM. Reason: I typically alternate
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Old 07-13-2014, 10:39 AM   #39
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My local Shells do 93 octane for the price of 89 on Tuesdays... not sure if that's just a regional thing, but that's the only day I fill up.
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Old 07-13-2014, 01:07 PM   #40
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My local Shells do 93 octane for the price of 89 on Tuesdays... not sure if that's just a regional thing, but that's the only day I fill up.
I have never heard of this before - you must have incredible luck.
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Old 07-13-2014, 01:07 PM
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