What octane do you use

[BmacIL]

That's because the EBM suffers a lot more from lower octane fuel than the GT. DI and FI do NOT like low octane fuel. The GT is something like a 1% power loss going from 93 to 87. I always ran 91 in my EBM, and I always run it in my GT (that's the highest we have around here).

Peak, yes. There is a noticeable and significant difference in midrange torque/power, however. I recall it being ~20-25 hp and you can feel it.

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[Hack]

Perhaps you don't understand detonation. Detonation occurs when you run low octane/poor quality fuel in a high performance engine built more than 20 years ago prior to modern ECUs.

Fixed.

 

[BmacIL]

Fixed.

You're mostly right. Only true if said engines have knock sensors. Not all modern engines do.

 

[jasonstang]

Fixed.

True electronics really allow these new high compression engine run okay on regular gas but why would you? ECU adjusting the timing and cam phases to outside the engine's optimum parameters so it won't run as efficient or powerful.
You wouldn't put Prius tires on a high performance car even thought they will roll just fine, would you?

 

[r1lovin]

I run 91 octane on my pc kit lund tuned. At 9.5 psi it's still adding 15° of timing.

 

[Hack]

You're mostly right. Only true if said engines have knock sensors. Not all modern engines do.

The post I quoted was about performance engines. Also, people in this thread are asking about using the lowest recommended octane vs. using a higher than recommended octane. If you run the minimum recommended octane in your car, you will not have a problem related to octane.

True electronics really allow these new high compression engine run okay on regular gas but why would you? ECU adjusting the timing and cam phases to outside the engine's optimum parameters so it won't run as efficient or powerful.
You wouldn't put Prius tires on a high performance car even thought they will roll just fine, would you?

Ford recommends 93 octane in the GT350, but my understanding is that in California 91 is the highest available. That's an example of a reason for running a lower than recommended octane. There's a single gas station in my area that has 93 available and it is a bit of a pain to always fill there, so at times I do fill with 91 as well. When it's below 50 F as a high temperature I would be very surprised if there's a difference between how 93 and 91 function in my engine. Seat of the pants I definitely haven't noticed a difference. I wouldn't blame someone for always using 91 in the GT350, just due to the knowledge that many, many of them will have 91 in every tank full. When I have a track day I do make more of an effort to get 93 in there, but I realize there's no reason that it's necessary. People in CA run track days all the time no problem.

Prius tires? Obviously there's no similarity there. That's like filling the tank with kerosene, and no one here is suggesting that.

 

[jasonstang]

Ford recommends 93 octane in the GT350, but my understanding is that in California 91 is the highest available. That's an example of a reason for running a lower than recommended octane. There's a single gas station in my area that has 93 available and it is a bit of a pain to always fill there, so at times I do fill with 91 as well. When it's below 50 F as a high temperature I would be very surprised if there's a difference between how 93 and 91 function in my engine. Seat of the pants I definitely haven't noticed a difference. I wouldn't blame someone for always using 91 in the GT350, just due to the knowledge that many, many of them will have 91 in every tank full. When I have a track day I do make more of an effort to get 93 in there, but I realize there's no reason that it's necessary. People in CA run track days all the time no problem.

Prius tires? Obviously there's no similarity there. That's like filling the tank with kerosene, and no one here is suggesting that.

91 is fine to run in the GT350 with 12:1 compression. My Monster 1200 with 600cc cylinders run 91 with 12.5:1 compression with no problem. The Coyote is 11:1 compression and 87 is simply too low. It would be like running 89 in your Voodoo.

 

[ob1]

92 non ethanol is what I like. $1.25 more a gallon but she likes it!

 

[thumper]

where i live in canada, 91 octane is the highest you can get at the pump, and ford sells the gt350 here... i wonder what the canadian gt350 owners manual says.

 

[Kevin08]

Here you go sir:

www.toptiergas.com/retailers/

So basically the most common gas.

 

[SnoopisTDI]

where i live in canada, 91 octane is the highest you can get at the pump, and ford sells the gt350 here... i wonder what the canadian gt350 owners manual says.

They also sell cars in the winter with tires which aren't warranted below 45degF. :shrug:

 

[Blk2015GT]

Forum engineers :doh:

I guess all those guys at Ford with hundreds of years of engineering experience and dozens of combined degrees know much less than forum members :shrug:

If you do some spirited driving sure toss some 91/93 in a GT. For daily to the office and groceries is that 20-25hp REALLY that important to spend $.50/gallon (or more in some areas) more just because. The manual CLEARLY says 87 for a reason based on those hundreds of years of combined engineering knowledge. Not alleged forum engineers.

 

[mada808]

well, I tested this Octane debate out and noticed exactly zero difference in fuel economy or performance(although I didn't expect to notice a performance difference being at only a ~1% loss). I still averaged 16.1 mpg which is exactly what I get on premium fuel. I drive to work and back ONLY and it's generally back roads averaging 45 mph.

 

[BmacIL]

Forum engineers :doh:

I guess all those guys at Ford with hundreds of years of engineering experience and dozens of combined degrees know much less than forum members :shrug:

If you do some spirited driving sure toss some 91/93 in a GT. For daily to the office and groceries is that 20-25hp REALLY that important to spend $.50/gallon (or more in some areas) more just because. The manual CLEARLY says 87 for a reason based on those hundreds of years of combined engineering knowledge. Not alleged forum engineers.

Actual engineer here, and former Ford powertrain engineer.

The engine runs perfectly fine on 87, which is why it's the recommended fuel. It will run in a healthy way for its entire live on 87. That doesn't mean there aren't legitimate performance benefits on 93.

 

[Zebra]

Mine is tuned to run 93. Unless you're high altitude it really sucks to only have 91 available.

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