What Octane are you using for the 5.0?

[Free Agent]

I'd also like to see the testing I suggested run at 2 different atmospheric conditions, say one at 50 degrees with low humidity and then again at 90 degrees with high humidity. Air temp./humidity this time of year is great and I'm willing to bet there isn't as big difference in HP between the two. But when it is hot and humid outside and the computer senses knock and pulls timing because of the thinned out air I am guessing the difference will be larger.

I love how my engines run this time of year in the cold/cool air. They always feel a lot slower in the summer as they suck in the hot humid "thinner" air. Some of this "feel" a lot of people talk about could be temperature dependent.

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[Budwise]

You might not feel the difference but if you data logged your car running less than 91 you'd see a massive difference. Your car is constantly having to detect knock and then pull timing to prevent damage to the motor. It OK in a pinch but not good if you plan to keep the car long term. The stock tune is for 91 and above, run less or even worse run less and run it hard and you're rolling the dice for the long term longevity of your motor.

 

[Free Agent]

You might not feel the difference but if you data logged your car running less than 91 you'd see a massive difference. Your car is constantly having to detect knock and then pull timing to prevent damage to the motor. It OK in a pinch but not good if you plan to keep the car long term. The stock tune is for 91 and above, run less or even worse run less and run it hard and you're rolling the dice for the long term longevity of your motor.

I have tracked a lot of knock retard and timing in my GTO with a handheld and yes it is easy to see the difference between fuels especially in those situations I noted above when DA is well above 3000 ft, the engine is hot and it pulls timing like a SOB when IAT's shoot north of 130 degrees. Good points.

 

[JimmyTwoTimes]

You might not feel the difference but if you data logged your car running less than 91 you'd see a massive difference. Your car is constantly having to detect knock and then pull timing to prevent damage to the motor. It OK in a pinch but not good if you plan to keep the car long term. The stock tune is for 91 and above, run less or even worse run less and run it hard and you're rolling the dice for the long term longevity of your motor.

What do you mean about the "long term longevity of your motor"? I very very very rarely tax my engine at all, but I do plan on driving the thing into the ground, getting 250,000 miles out of it. But the vast majority of my driving is in very sedate, very low-g conditions, mostly below 2,000 rpm and almost entirely below 4,000 rpm. I don't imagine that lower octane fuel will cut into my engine life much.

 

[AdrianMAK]

93Oct, price of fuel is low enough that the difference on a 15 gallon tank is a couple of bucks.
93 burns cleaner, will make more power, and should even mean better MPG for the most part. I am programmed to run 93 oct on anything performance related. It doesn't really make sense to run any lower. From the factory a Mustang GT is a performance vehicle.

 

[MSamuels]

EXACTLY what I said. I mean everyone here is obsessed with performance losses and how they might be marginal but you ever listen to the motor running on 87? Its constantly running rough and compensating for knock. Like I said garbage gas. Use 89 at an absolute minimum.

 

[Khyber]

87 only. i see no reason to run any higher in it. at $1.90 a gallon I can't beat $27 fill up on this beast.

There area lot of numbers being thrown around but ford confirmed last week only the eco boost loses torq and no hp on 87. the 5.0 loses like 1hp but retains all torq. anyone who wants to run higher than 87 that's fine too.

 

[packerfan]

The 5.0 in the 11 -14 cars lost like 25 hp on 87. Dont see why it would be any different for the 15.

 

[JimmyTwoTimes]

The 5.0 in the 11 -14 cars lost like 25 hp on 87. Dont see why it would be any different for the 15.

Because Ford said so.

Ford said that the Coyote in the 2011 Mustang was rated at 390 hp on 87 octane. Ford also said that the Coyote in the 2015 Mustang loses "1%" of peak power on 87 octane.

 

[packerfan]

I wonder why ford switched from listing actual power figures on 87 to a percentage loss?

 

[blitzburgh]

Well this isn't going to go anywhere. My 2 cents is my car is one of the most expensive things I have. I am not going to trip over 400.00 a year to run 91. I don't do it for the added HP I feel its better on the internals. Whoever wants to run 87 do it.

If you want to spend over 400.00 a month on alcohol lol do that too, whatever floats your boat.

 

[Need4Speed15]

I have never run less then 93 in my 12 and now my 15.

The engine has adaptive learning and knock sensors so if you want to run 87 go ahead, but performance will suffer. You guys know its an 11.1 motor, right?

In my eyes....performance and safety far outweigh saving pennies at the pump!

 

[Budwise]

What do you mean about the "long term longevity of your motor"? I very very very rarely tax my engine at all, but I do plan on driving the thing into the ground, getting 250,000 miles out of it. But the vast majority of my driving is in very sedate, very low-g conditions, mostly below 2,000 rpm and almost entirely below 4,000 rpm. I don't imagine that lower octane fuel will cut into my engine life much.

Knock aka Ping often happens at low rpm during slight engine load in situations like going up a hill in 6th gear for example. At the end of the day its your car and your choice though. I'm merely informing people so they can in turn make informed decisions.

 

[Free Agent]

I'd also like to know what were the testing conditions when Ford says loses 1% power. I guarantee on a hot 90 plus degree day with a dew point north of 70 degrees and IAT's soaring past the 100 degree mark in traffic due to heat soak that a 5.0 running 87 is going to be pulling a lot more timing than one running 93. In those situations there is no way you are only losing 4.35 HP. If that was the case every drag racer in the country would be running 87 octane.

Bottom line….

You can run 87 just fine, just don't expect to get the full performance from your engine and know that in certain situations you may be subjecting your car to detonation/knock. Also know that during certain times of the year you are going to have a greater loss due to air density and your stock computer pulling timing to protect your engine.

For me I'll run 93 (available for me and only 30 cents more a gallon) get every last HP Ford claims from my stock engine and have the knowledge that under certain conditions and engine loads that I am protecting my engine from detonation/knock.

Now I'm outta here until another thread like this one invariably pops up again in a couple of weeks.

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