Has no one dynoed the s550 GT with 87 vs 91 octane?

[clevernickname]

I will start off this post by saying this forum has some of the most helpful and normal people out of many forums I frequent. I haven't seen much "fanboyism" surprisingly, and people are quite down to earth in the mustang versus forums, stating pros and cons of the new SS for example. But I am so frustrated that every time the octane thread comes up, half the posts are "93 unleashes the power, I FEEL IT", and the other half are, "you bought a 40k car and you can't afford 91 octane? lawl u poor or sumtin?" Ok, exaggeration, and I'm not sure if anyone else is semi-annoyed at all those posts, but I would love to see some actual numbers.

Cause if anyone can feel the difference in a double blind test of 5-10 hp, then they must be in the top .00000000000000000001% of driving enthusiasts. And that's assuming 91 or 93 octane is actually giving more power.

Let's not forget at how many people will claim an axleback exhaust adds power, or 3'' pipes will add 20hp, intake and tune and I'm basically a gt350, etc.

Sorry I'm probably ranting over nothing, so

tl;dr - any actual numbers? "feels better" doesn't seem very scientific.

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[Semi]

No, nobody did. I enjoyed your rant and I'm new to the mustang mod world, just figuring out where I'm going to get the money.

But nobody's going to tune anything on anything less than the highest octane they can or 91 as that's usually as much as you're going to find at the stations in my state.

What's the point right?

Now if you own a dyno and you wanna goof off ya never know.

 

[DarkestHour]

There's numbers in data logs showing knock events. Don't buy such an expensive car if you can't afford 91 octane. You probably have some serious financial issues in that case.

 

[foghat]

There's numbers in data logs showing knock events. Don't buy such an expensive car if you can't afford 91 octane. You probably have some serious financial issues in that case.

Data logs of the factory tune?

It is perfectly fine to use 87.

 

[AmericanLegend]

I would like to see this as well. Same car, same dyno, same environmental conditions, etc.

I've used both 87 and 93 octane. I "think" I feel more pull in the mid range (3000-4500 rpm) with 93. I also feel like the exhaust burbles more with 93?

I'm currently of the mind set that it's not worth $7 per tank to give up, or maybe just feel like I'm giving up power using 87 vs 93.

I agree, It would be very nice to see the dyno numbers comparing 87 vs 93 though....

 

[Lucky13Cat]

Data logs of the factory tune?

It is perfectly fine to use 87.

exactly:amen:

 

[SR56]

I miss the days when it was only a dime difference between each grade. To go from 87, skip 89,and go to 93 was only 20 cents more. We got gouged somewhere along the way.

 

[mustang1]

I think the 435 hp has some fine print, * with 93 octane. I have been paying extra for 93 octane but I just noticed 93 octane is now 70 cents a gallon more. And I am suspicious 93 octane is sometimes stale.

 

[SR56]

I think the 435 hp has some fine print, * with 93 octane. I have been paying extra for 93 octane but I just noticed 93 octane is now 70 cents a gallon more. And I am suspicious 93 octane is sometimes stale.

If there's a Costco near you that would be a good place to get your 93. Top tier rated, high tank turnover, and it runs about 40 cents or so a gallon less than competitors.

The closest one to me doesn't make it worth the trip, sadly.

 

[slowbutfast]

When my car was stock, I would run 87 on long hauls. There really isn't much of a performance difference. In my previous cars that I used to datalog; weather always played a part with detonation. So I usually only consider running 87 in colder weather.

 

[magnetic16gt]

I find it interesting that the manual calls for 87 octane. My '14 said "91 octane recommended for optimal performance" or something along those lines.

I've tried premium vs 87 on both my '14 and '16. The only financial issue I've seemed to have with using 87 while its 80 cents less a gallon is having a lot more money in my pocket over 50k miles.

 

[MRose]

Don't buy such an expensive car if you can't afford 91 octane. You probably have some serious financial issues in that case.

The mustang is not an expensive car. Almost every 4x4 truck and SUV on the road costs more.

 

[Hack]

I will start off this post by saying this forum has some of the most helpful and normal people out of many forums I frequent. I haven't seen much "fanboyism" surprisingly, and people are quite down to earth in the mustang versus forums, stating pros and cons of the new SS for example. But I am so frustrated that every time the octane thread comes up, half the posts are "93 unleashes the power, I FEEL IT", and the other half are, "you bought a 40k car and you can't afford 91 octane?

tl;dr - any actual numbers? "feels better" doesn't seem very scientific.

Great question! I'd love to see a dyno test. And I'd love to see it done at 100F, 80F, 60F, and 40F. I would be surprised if there's much if any difference at ~70F or below.

I can say that I started using higher octane and then I switched to 87 (back when I had a GT). I could never tell a difference. I'm in MN and the weather is cool most of the year here. There's probably a difference on a hot day in bumper to bumper traffic when the A/C is cranked, but most days I would be very surprised if it's more than say 10 hp or something. Also, I'm sure not going to spend more for higher octane when it's cold and I'm traction limited anyway.

I put the low limit 91 octane in my GT350 when it's cool/cold as well.

 

[jasonstang]

Someone did a comparison on the first gen coyote. The peak difference is about 5hp but midrange is about 40hp. I need to go find the dyno chart again.

 

[DarkestHour]

Data logs of the factory tune?

It is perfectly fine to use 87.

And do you know why that is? It's because the car senses knock events and removes timing using something called OAR. When this value is positive it is then doing blanket retarding of timing to the base timing tables. What happens when you retard timing? The car doesn't perform as well. What happens to get to this point? Knock. Knock is never "perfectly fine".

When the value is negative, this means the car is doing a blanket advance of timing to the base timing tables. The counter reaches this point when the car repeatedly does not experience knock when the ECM advances timing up to a set limit/time period/load.

I really don't get it. Don't buy an expensive car if you can't run 91 octane. It's not whether the factory calibration allows it, it's the principle.

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