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2018 GT MPG 87 vs. 93 octane

Bikeman315

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13razorbackfan

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If it wasn't for this forum I would have never known or never sought out different fuels because I'm not a mechanic and I don't race. The only thing I have ever paid attention to was ethanol because of all my landscaping equipment. This forum is great
 

3star2nr

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To pay for free hospitals. Free education. Actually we get paid to go to school when we turn 18.
56 (I think) weeks payed maternity leave pr. child. Alot of good stuff when U have a baby really. 690 USD every quarter from 0-2yo. That amount drops 130 USD when they are 3-6. Another 130 USD down when they are 7-14.
We get 6 weeks payed off work each year.
We have so many benefits, but of course the money have to come from somewhere. But the salary is high too I guess. I get 31,5 USD pr. hour, and I'm a carpenter. That's not bad, for the effort I put in. :cwl:

Back on the car related stuff. Since the Mustang is well into the 100k USD, U don't see a lot of them here. I have now seen 36 S550's. It's a real headturner here. :rockon:
If my taxes went to all that that would be awesome... Instead it goes to bullshit like building conference rooms in desserts, 10k per gallon to ship oil to the middle east all so we can fight Saudi Arabia and israels wars for them.... Or go into developing engineering we just give to china, India and saudi Arabia basically for free... Then have the sack to complain about "intellectual property theft"

Denmark is A tiny country relative to the USA so you will pay higher taxes because you have less people paying into it... Its simple math...

Obw you aren't the only nation paying higher fuel costs... It has nothing to do with immigrants and everything to do with Wall Street speculation and fuel companies artificially inflating prices...

Blamming People with zero political power or the ability to change anything may make you feel good but gets you nothing... Kind of like trying to get to work using a rocking chair... Good luck with that
 

jpogi

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I had first hand experience with an older 9:1 CR Nissan engine about octane grade. When the first 100 RON (94 AKI) became available in my home country, I eagerly used it.

It resulted with my car running slugish, black exhaust, moist spark plug tips. Went back to 91 RON (87 AKI) and the car ran fine, the spark plugs cleaned by themselves to dry brown. My exhaust tip also cleared up!

So I researched and actually found out that lower octane burns easier as it has lower flash point. While high octane is harder to ignite. So I am actually a big fan of low octane fuel, specially in winter.

That said... I will only run 91-93 AKI on the Cayote GEN 3. It has a freaking 12.0:0 compression ratio. I know DI fine mist makes it less prone to auto ignition but still, that fuel gets squished hard before TDC and will still be prone to auto-detonate.

Why the heck would Ford add 2 more sets of knock sensors? The fact that knock sensors senses knock, means some sort small pings already happened.

With the irreplaceable plasma cylinder lining we got, I wouldn’t add anymore chances of having pinging. I just daily drive, but there are instances that I may have to downshift or punch the throttle into higher rpms. I don’t want my knock sensors sensing knock on my engine.
 

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13razorbackfan

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I had first hand experience with an older 9:1 CR Nissan engine about octane grade. When the first 100 RON (94 AKI) became available in my home country, I eagerly used it.

It resulted with my car running slugish, black exhaust, moist spark plug tips. Went back to 91 RON (87 AKI) and the car ran fine, the spark plugs cleaned by themselves to dry brown. My exhaust tip also cleared up!

So I researched and actually found out that lower octane burns easier as it has lower flash point. While high octane is harder to ignite. So I am actually a big fan of low octane fuel, specially in winter.

That said... I will only run 91-93 AKI on the Cayote GEN 3. It has a freaking 12.0:0 compression ratio. I know DI fine mist makes it less prone to auto ignition but still, that fuel gets squished hard before TDC and will still be prone to auto-detonate.

Why the heck would Ford add 2 more sets of knock sensors? The fact that knock sensors senses knock, means some sort small pings already happened.

With the irreplaceable plasma cylinder lining we got, I wouldn’t add anymore chances of having pinging. I just daily drive, but there are instances that I may have to downshift or punch the throttle into higher rpms. I don’t want my knock sensors sensing knock on my engine.
So I take it the lower octane the higher the chances of it knocking?
 

mustang1

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... That said... I will only run 91-93 AKI on the Cayote GEN 3. It has a freaking 12.0:0 compression ratio. I know DI fine mist makes it less prone to auto ignition but still, that fuel gets squished hard before TDC and will still be prone to auto-detonate.

Why the heck would Ford add 2 more sets of knock sensors? The fact that knock sensors senses knock, means some sort small pings already happened.

With the irreplaceable plasma cylinder lining we got, I wouldn’t add anymore chances of having pinging. I just daily drive, but there are instances that I may have to downshift or punch the throttle into higher rpms. I don’t want my knock sensors sensing knock on my engine.
87 octane is fine. Ford added the extra set of knock sensors to support superchargers.
 

jpogi

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87 octane is fine. Ford added the extra set of knock sensors to support superchargers.
I know it's fine, the manual says so. But I'm keeping this car until forever. And running 87 is cutting too close for higher chances of pre-ignition.

As I've mentioned earlier, knock sensors retards the timing only after it senses pinging. That means some amount of harmless pre-detonation already happened. But they will take it's toll. Not a problem if you don't plan to keep your car until it runs no more, unlike me.

For me, running 91-93 is no different from changing oil regularly. It is a preventive maintainance, and it will cost some $$.
 

Qcman17

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I had been running 94 but once i realized this car is okay in general on 87 I dropped to 91 and it feels the same to me. That saved me $.05 per liter right there. My Camaro required 91 as a minimum even before I had it tuned later to run only 94. I have a hard time with putting 87 in this car as it just seems wrong to me with the 12:1 but no doubt Ford knows what is okay or not. On the other hand I don't daily drive and park mine during the winter months to boot so the price of gas doesn't matter much in that sense either. So for now I'm going to stick with 91.
 

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mustang1

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I know it's fine, the manual says so. But I'm keeping this car until forever. And running 87 is cutting too close for higher chances of pre-ignition.

As I've mentioned earlier, knock sensors retards the timing only after it senses pinging. That means some amount of harmless pre-detonation already happened. But they will take it's toll. Not a problem if you don't plan to keep your car until it runs no more, unlike me.

For me, running 91-93 is no different from changing oil regularly. It is a preventive maintainance, and it will cost some $$.

You can still keep the car forever if 87 causes too much pre-ignition and the car requires a new short block. :headbang:

JK. I don't have an opinion on 87 / 93.
 

Dfeeds

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87 octane is fine. Ford added the extra set of knock sensors to support superchargers.
Source?

The main and only "reasonable" reason why they have to make higher octane fuel is to prevent auto ignition.
Ding ding. Calling it "premium" is a silly marketing gimmick. Auto ignition is when the air/fuel mixture ignites without a spark, due to too much heat and compression. This is bad in ICE engines. If it occurs too early, it will try to push the piston down as it's traveling up, causing damage. Higher octane resists this. Higher compression means more power, so running higher octane enables the engine to have a higher compression ratio. However, the mixture needs to burn so that maximum cylinder pressure occurs at the optimum moment of the stroke. Higher octane fuel takes longer to burn, so it requires more advanced timing so the mixture ignites earlier. If it doesn't ignite early enough, then the mixture will burn after top dead center, wasting energy and losing power. So 93 isn't better than 87. Which octane is best is entirely dependent on the design of the engine because it's a balancing act. Although, anyone who says the engine was designed around 87 octane is kidding themselves. The engine isn't designed with a fuel's octane rating as its primary influence. It would be the compression ratio, with changes in timing made to accommodate different octane fuel. If the engine were designed around 87, then the jump to e85 wouldn't be so substantial. In fact, e85 providing such a nice power bump implies that 93 is as much of a compromise as 87 is. An example of an engine preferring 87 would be the pushrod 5.0l with its 9:1 CR. Running 93 would just result in wasted energy and unburnt fuel.

This leads me to the following. The 12:1 compression ratio is a theoretical number because the CR is dynamic. There are several factors that influence this but, for the sake of 87 vs 93 octane, I'll focus on the cam timing (hello VCT). The sooner the intake valve closes, the more cylinder pressure occurs and the more low end power is made. This hurts top end power because the engine also has to work harder to compress the mixture, and this is why vct offers so much flexibility (like running 87 octane). If the intake valve closes later then there's less cylinder pressure and reduced risk of 87 octane fuel auto igniting. Direct injection further helps because of the cooler charge and more controlled fuel delivery because it's independent of the valve timing. But you're giving up some good low to mid range power. Also, at high engine speeds, the amount of time the mixture is fully compressed is very short, so auto ignition is less likely to occur. All the above is why peak horsepower is not affected as much by running 87. Oh if only peak horsepower were everything...

I guess that's a bit off topic, but there was plenty of arguing about the power benefits so... ya. As for MPG, a richer mixture is cooler and resists auto ignition so if ecu richens the mixture for 87 then it would get worse gas mileage. Although, if I had to guess, it wouldn't be by very much when cruising around and would only show if driven hard on a regular basis. I, personally, wouldn't use mpg as my reason to pick 87 or 93.
 

13razorbackfan

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Ding ding. Calling it "premium" is a silly marketing gimmick. Auto ignition is when the air/fuel mixture ignites without a spark, due to too much heat and compression. This is bad in ICE engines. If it occurs too early, it will try to push the piston down as it's traveling up, causing damage. Higher octane resists this. Higher compression means more power, so running higher octane enables the engine to have a higher compression ratio. However, the mixture needs to burn so that maximum cylinder pressure occurs at the optimum moment of the stroke. Higher octane fuel takes longer to burn, so it requires more advanced timing so the mixture ignites earlier. If it doesn't ignite early enough, then the mixture will burn after top dead center, wasting energy and losing power. So 93 isn't better than 87. Which octane is best is entirely dependent on the design of the engine because it's a balancing act. Although, anyone who says the engine was designed around 87 octane is kidding themselves. The engine isn't designed with a fuel's octane rating as its primary influence. It would be the compression ratio, with changes in timing made to accommodate different octane fuel. If the engine were designed around 87, then the jump to e85 wouldn't be so substantial. In fact, e85 providing such a nice power bump implies that 93 is as much of a compromise as 87 is. An example of an engine preferring 87 would be the pushrod 5.0l with its 9:1 CR. Running 93 would just result in wasted energy and unburnt fuel.

This leads me to the following. The 12:1 compression ratio is a theoretical number because the CR is dynamic. There are several factors that influence this but, for the sake of 87 vs 93 octane, I'll focus on the cam timing (hello VCT). The sooner the intake valve closes, the more cylinder pressure occurs and the more low end power is made. This hurts top end power because the engine also has to work harder to compress the mixture, and this is why vct offers so much flexibility (like running 87 octane). If the intake valve closes later then there's less cylinder pressure and reduced risk of 87 octane fuel auto igniting. Direct injection further helps because of the cooler charge and more controlled fuel delivery because it's independent of the valve timing. But you're giving up some good low to mid range power. Also, at high engine speeds, the amount of time the mixture is fully compressed is very short, so auto ignition is less likely to occur. All the above is why peak horsepower is not affected as much by running 87. Oh if only peak horsepower were everything...

I guess that's a bit off topic, but there was plenty of arguing about the power benefits so... ya. As for MPG, a richer mixture is cooler and resists auto ignition so if ecu richens the mixture for 87 then it would get worse gas mileage. Although, if I had to guess, it wouldn't be by very much when cruising around and would only show if driven hard on a regular basis. I, personally, wouldn't use mpg as my reason to pick 87 or 93.
Wow what awesome info. Learned a lot
 

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Ding ding. Calling it "premium" is a silly marketing gimmick. Auto ignition is when the air/fuel mixture ignites without a spark, due to too much heat and compression. This is bad in ICE engines. If it occurs too early, it will try to push the piston down as it's traveling up, causing damage. Higher octane resists this. Higher compression means more power, so running higher octane enables the engine to have a higher compression ratio. However, the mixture needs to burn so that maximum cylinder pressure occurs at the optimum moment of the stroke. Higher octane fuel takes longer to burn, so it requires more advanced timing so the mixture ignites earlier. If it doesn't ignite early enough, then the mixture will burn after top dead center, wasting energy and losing power. So 93 isn't better than 87. Which octane is best is entirely dependent on the design of the engine because it's a balancing act. Although, anyone who says the engine was designed around 87 octane is kidding themselves. The engine isn't designed with a fuel's octane rating as its primary influence. It would be the compression ratio, with changes in timing made to accommodate different octane fuel. If the engine were designed around 87, then the jump to e85 wouldn't be so substantial. In fact, e85 providing such a nice power bump implies that 93 is as much of a compromise as 87 is. An example of an engine preferring 87 would be the pushrod 5.0l with its 9:1 CR. Running 93 would just result in wasted energy and unburnt fuel.

This leads me to the following. The 12:1 compression ratio is a theoretical number because the CR is dynamic. There are several factors that influence this but, for the sake of 87 vs 93 octane, I'll focus on the cam timing (hello VCT). The sooner the intake valve closes, the more cylinder pressure occurs and the more low end power is made. This hurts top end power because the engine also has to work harder to compress the mixture, and this is why vct offers so much flexibility (like running 87 octane). If the intake valve closes later then there's less cylinder pressure and reduced risk of 87 octane fuel auto igniting. Direct injection further helps because of the cooler charge and more controlled fuel delivery because it's independent of the valve timing. But you're giving up some good low to mid range power. Also, at high engine speeds, the amount of time the mixture is fully compressed is very short, so auto ignition is less likely to occur. All the above is why peak horsepower is not affected as much by running 87. Oh if only peak horsepower were everything...

I guess that's a bit off topic, but there was plenty of arguing about the power benefits so... ya. As for MPG, a richer mixture is cooler and resists auto ignition so if ecu richens the mixture for 87 then it would get worse gas mileage. Although, if I had to guess, it wouldn't be by very much when cruising around and would only show if driven hard on a regular basis. I, personally, wouldn't use mpg as my reason to pick 87 or 93.
A lot of engine science right here...thanks for the info.
 

BlackandBlue

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Ding ding. Calling it "premium" is a silly marketing gimmick. Auto ignition is when the air/fuel mixture ignites without a spark, due to too much heat and compression. This is bad in ICE engines. If it occurs too early, it will try to push the piston down as it's traveling up, causing damage. Higher octane resists this. Higher compression means more power, so running higher octane enables the engine to have a higher compression ratio. However, the mixture needs to burn so that maximum cylinder pressure occurs at the optimum moment of the stroke. Higher octane fuel takes longer to burn, so it requires more advanced timing so the mixture ignites earlier. If it doesn't ignite early enough, then the mixture will burn after top dead center, wasting energy and losing power. So 93 isn't better than 87. Which octane is best is entirely dependent on the design of the engine because it's a balancing act. Although, anyone who says the engine was designed around 87 octane is kidding themselves. The engine isn't designed with a fuel's octane rating as its primary influence. It would be the compression ratio, with changes in timing made to accommodate different octane fuel. If the engine were designed around 87, then the jump to e85 wouldn't be so substantial. In fact, e85 providing such a nice power bump implies that 93 is as much of a compromise as 87 is. An example of an engine preferring 87 would be the pushrod 5.0l with its 9:1 CR. Running 93 would just result in wasted energy and unburnt fuel.

This leads me to the following. The 12:1 compression ratio is a theoretical number because the CR is dynamic. There are several factors that influence this but, for the sake of 87 vs 93 octane, I'll focus on the cam timing (hello VCT). The sooner the intake valve closes, the more cylinder pressure occurs and the more low end power is made. This hurts top end power because the engine also has to work harder to compress the mixture, and this is why vct offers so much flexibility (like running 87 octane). If the intake valve closes later then there's less cylinder pressure and reduced risk of 87 octane fuel auto igniting. Direct injection further helps because of the cooler charge and more controlled fuel delivery because it's independent of the valve timing. But you're giving up some good low to mid range power. Also, at high engine speeds, the amount of time the mixture is fully compressed is very short, so auto ignition is less likely to occur. All the above is why peak horsepower is not affected as much by running 87. Oh if only peak horsepower were everything...

I guess that's a bit off topic, but there was plenty of arguing about the power benefits so... ya. As for MPG, a richer mixture is cooler and resists auto ignition so if ecu richens the mixture for 87 then it would get worse gas mileage. Although, if I had to guess, it wouldn't be by very much when cruising around and would only show if driven hard on a regular basis. I, personally, wouldn't use mpg as my reason to pick 87 or 93.

That’s all great info.

The part about the piston being pressed down is slightly misleading though.

The part of higher compression detonation that causes damage is the combining flame fronts. The energy pushing piston to push down the other way is not what causes the problem.

This is why a lower compression engine can knock(ping) its whole life and a higher compression engine will start to eat itself up over a shorter amount of time.

A higher compression engine can have multiple flame fronts of detonation inside the cylinder. These flame fronts can combine into a point to create serious damage inside the the cylinder. It’s the multiplying effect that causes problem.
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