Octane on 17' GT

[Ecoboosted]

I used 87 for 2 years with no ill effects. Now that I got my FR PP2 on it requires 91. Since I can't find 91 I have to use 93. No complaints just wish I could find 91

Sponsored

 

[Kinjirra]

Used 93 from day one...and I DD and road trip mine.

seriously if you guys are worried about MPG and gas price at a few bucks extra a fillup why did you buy a thirsty v-8? Not bashing I just don't understand the logic...get all the looks and goodies with a more efficient engine.

 

[jasonstang]

I’ve had my 2017 GT convertible for 8 months now and approaching 5000 miles. I use 87 octane non-ethanol fuel from Murphy USA. I get 22+ mpg in town and 26+ mpg on the highway. There has been no performance issues but I do not drive the car hard. More easy cruising than anything else. I stick with non-ethanol because it provides a more smooth idle at red lights.

My 2 cents!

That poor engine is running all retarded timing carboning up the cylinders.

 

[Draklia]

I think some of you might be surprised what the knock sensors are doing on a WOT datalog with 87 octane in the tank.

 

[millhouse]

Used 93 from day one...and I DD and road trip mine.

seriously if you guys are worried about MPG and gas price at a few bucks extra a fillup why did you buy a thirsty v-8? Not bashing I just don't understand the logic...get all the looks and goodies with a more efficient engine.

.50 per gallon equates to $7.50 per tank. At 20k miles per year, I save $500+ per year. If you could save $500/year (~$42/month) by changing something that is not noticeable, why wouldn't you?

And for the record, I've yet to see any comparisons of the S550 coyote running 87 and 93 octane during after each has had time to auto tune.

That poor engine is running all retarded timing carboning up the cylinders.

Bullshit.

 

[jasonstang]

.50 per gallon equates to $7.50 per tank. At 20k miles per year, I save $500+ per year. If you could save $500/year (~$42/month) by changing something that is not noticeable, why wouldn't you?

And for the record, I've yet to see any comparisons of the S550 coyote running 87 and 93 octane during after each has had time to auto tune.

Except you're not really saving that much as lower octane meaning engine will not run the fuel as efficient. As a result, you mpg drops so you might end up paying the same amount per year but you just fill up more frequently.

 

[millhouse]

Except you're not really saving that much as lower octane meaning engine will not run the fuel as efficient. As a result, you mpg drops so you might end up paying the same amount per year but you just fill up more frequently.

My MPG is identical between 87 and 93 octane...as it is for everyone else with a stock S550 5.0 mustang. Anyone that concludes otherwise needs to change their fuel brand.

And for the record, I average 20mpg on 87 (and 93) octane. In order to offset the $.50 price difference I would need to be able to average 25mpg on 93...which needless to say is not going to happen.

 

[Taneras]

.50 per gallon equates to $7.50 per tank. At 20k miles per year, I save $500+ per year. If you could save $500/year (~$42/month) by changing something that is not noticeable, why wouldn't you?

Most people would notice ~20rwhp/~20rwtq in the midrange, though. That might not be enough to justify the extra cost to you or others but there is a noticeable difference.

And for the record, I've yet to see any comparisons of the S550 coyote running 87 and 93 octane during after each has had time to auto tune.

There's one in this thread. The 87 vs 93 comparison lists the "best" runs (telling us that there were multiple runs for each).

Moreover why are you assuming that in these tests the mustang wasn't allowed time to adjust to the new fuel type? Sounds like you just want to justify your choice for 87 octane.

You don't need to justify it to anyone here, but creating doubt when there's no good reason isn't helpful to the community.

 

[texasboy21]

My MPG is identical between 87 and 93 octane...as it is for everyone else with a stock S550 5.0 mustang.

My GT PP is stock and I noticed a 2-4mpg decrease when I was forced to run 87 instead of the usual 93 for three tanks. Same brand gas. Even the same station, just lower octane. I also noticed a decrease in power below 5K rpms.

The owners manual says you can run regular, which doesnt mean anything other than the ECU can compensate/adjust based on the octane level - just like an aftermarket flex fuel tune.

Ford states the advertised 435HP was achieved with 93 octane. If the same power level could be achieve with 87, do you think Ford would have the disclaimer?

 

[Taneras]

My GT PP is stock and I noticed a 2-4mpg decrease when I was forced to run 87 instead of the usual 93 for three tanks. Same brand gas. Even the same station, just lower octane. I also noticed a decrease in power below 5K rpms.

While I haven't seen a 4mpg difference I have consistantly seen ~2mpg differences.

Sure its not enough to cover the 50 cent difference, but it does cut into it a decent bit. At the end of the day you're trying to balance 100-300 bucks (depending on how many miles you drive a year) and losing ~20rwhp/20rwtq in the mid range. I'm not going to criticize anyone for choosing the cheaper route, but for me there's no question that the extra power is more important.

I'm past all this, though, E85 is the way to go

 

[TJ91]

Guys in Canada, the difference between 87 and 91 is about 24cents a litre. So let's say to fill up we need 50L, at 1.15 for 87 that amounts to $57 to fill up on 87 where to fill up 50L of 91 at 1.34 is $67

And when you're filling 3 times a week. That makes a big difference. I've been pumping 91 but I pump 87 in the winter because I don't need that power.

As for the difference in feel, I agree with the mid range, you can feel a bit of sluggishness in comparison to running 91

 

[millhouse]

Most people would notice ~20rwhp/~20rwtq in the midrange, though. That might not be enough to justify the extra cost to you or others but there is a noticeable difference.



There's one in this thread. The 87 vs 93 comparison lists the "best" runs (telling us that there were multiple runs for each).

Moreover why are you assuming that in these tests the mustang wasn't allowed time to adjust to the new fuel type? Sounds like you just want to justify your choice for 87 octane.

You don't need to justify it to anyone here, but creating doubt when there's no good reason isn't helpful to the community.

The thread posted was for a S197 coyote. These engine have different heads, different cams, different tunes.

And simply changing fuel and throwing it on the dyno isn't suffient. From my understanding, you typically need to run the car through nearly a full tank of fuel for the timing to fully adjust to the new fuel types.

With that said, I certainly don't notice a 20hp degradation between the two fuels.

My GT PP is stock and I noticed a 2-4mpg decrease when I was forced to run 87 instead of the usual 93 for three tanks. Same brand gas. Even the same station, just lower octane. I also noticed a decrease in power below 5K rpms.

The owners manual says you can run regular, which doesnt mean anything other than the ECU can compensate/adjust based on the octane level - just like an aftermarket flex fuel tune.

Ford states the advertised 435HP was achieved with 93 octane. If the same power level could be achieve with 87, do you think Ford would have the disclaimer?

I would fine a new gas station...quick. I run the same route 5 days a week...every week. 87 to 93 octane results in EXACTLY the same fuel economy...verified via both the computer and fuel receipts.

And the owners manual says 87 octane is the recommended fuel.

"We recommend regular unleaded gasoline
with a pump (R+M)/2 octane rating of 87.
Some stations offer fuels posted as regular
with an octane rating below 87, particularly
in high altitude areas. We do not
recommend fuels with an octane rating
below 87.
To provide improved performance, we
recommend premium fuel for severe duty
usage, such as trailer tow."

While I haven't seen a 4mpg difference I have consistantly seen ~2mpg differences.

Sure its not enough to cover the 50 cent difference, but it does cut into it a decent bit. At the end of the day you're trying to balance 100-300 bucks (depending on how many miles you drive a year) and losing ~20rwhp/20rwtq in the mid range. I'm not going to criticize anyone for choosing the cheaper route, but for me there's no question that the extra power is more important.

I'm past all this, though, E85 is the way to go

Again, sorry...you need to change your gas station, or your tune is off from the rest of the community. I'm not the only person who gets identical fuel economy on 87 and 93.

And for the record, I would eat $100 difference. I just checked the pump today and there is a $.60 delta between 87 and 93. $600/year is nothing to scoff at....it's damn close to what I pay for insurance.

My point is, I won't fault anyone for using 93 octane...but let's not pretend that it offers something magical for the coyote. It offers a power increase that can't be felt...and no difference in fuel economy.

 

[Rocketman]

That poor engine is running all retarded timing carboning up the cylinders.

LOL this guy

My point is, I won't fault anyone for using 93 octane...but let's not pretend that it offers something magical for the coyote. It offers a power increase that can't be felt...and no difference in fuel economy.

So like a few others in this thread have stated, I typically run 87 during the week since I don't need max power in my traffic infested commute. However, if my fillup falls on a Thursday or Friday then I will put in 93 for the weekend. And if you can't feel the difference between 87 and 93 then you:

A. Aren't driving your car hard enough
B. Sticking your head in the sand
C. Your body and mind is not perceptive enough to know the difference, in which case I sort of envy you.

I ONLY fillup 87 and 93 at QT which is a top tier station for my findings. I will agree with you that mileage isn't really noticeably affected.

 

[millhouse]

LOL this guy



So like a few others in this thread have stated, I typically run 87 during the week since I don't need max power in my traffic infested commute. However, if my fillup falls on a Thursday or Friday then I will put in 93 for the weekend. And if you can't feel the difference between 87 and 93 then you:

A. Aren't driving your car hard enough
B. Sticking your head in the sand
C. Your body and mind is not perceptive enough to know the difference, in which case I sort of envy you.

I ONLY fill-up 87 and 93 at QT which is a top tier station for my findings. I will agree with you that mileage isn't really noticeably affected.

Honestly, having several 10 second cars….I could be a bit numb….and yes, I drive it hard daily. Still, I have yet to see any track or dyno evidence that the S550 loses any appreciable amount of power or torque across the band.

This thread makes me want to do a few trials. Surely there would a difference outside of the noise when doing some timed highway speed pulls in 5th gear.

Agreed on the top tier....I either fill up at Costco or QT myself.

Sponsored