What octane do you use

[Hack]

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.

Not really.

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.

Good post!

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.

Thanks for the information. The last comment is very vague, though and leaves a lot of room for people here to make assumptions. Mine would be that the performance benefits of 93 are virtually unnoticeable without sophisticated equipment and the benefits have nothing to do with engine longevity.

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[Hashbrownn]

So I just went through about 2 tanks of 93 last week recently. As I've mentioned, I've been running 87 since I bought the car. Absolutely no difference other than my tank of gas went from $28 to $40. Knocking? Pinging? I couldn't tell with my naked ears. MORE HP? RIGHT~~ because I go WOT everytime.

 

[BmacIL]

Not really.



Good post!



Thanks for the information. The last comment is very vague, though and leaves a lot of room for people here to make assumptions. Mine would be that the performance benefits of 93 are virtually unnoticeable without sophisticated equipment and the benefits have nothing to do with engine longevity.

They're not unnoticable, but as another pointed out, for most people it's not worth it. There are fuel economy gains, but not enough to offset the increased cost of fuel. There are torque gains in the mid-range that you absolutely can feel, and have been verified by dyno. Is that enough to pay the difference in fuel cost? Only you can decide. Agreed that 93 does not improve engine longevity. Higher octane allows the engine to run a more aggressive map (timing) without degrading longevity. That is the important part.

 

[15wile]

I run 92 (that's what Wawa sells as Premium for some reason -- but it's super cheap) sometimes, and 93 other times. Never noticed a difference, really.

 

[jasonstang]

So I just went through about 2 tanks of 93 last week recently. As I've mentioned, I've been running 87 since I bought the car. Absolutely no difference other than my tank of gas went from $28 to $40. Knocking? Pinging? I couldn't tell with my naked ears. MORE HP? RIGHT~~ because I go WOT everytime.

Have you calculated dollar per mile instead of dollar per tank?

 

[jon2002]

They're not unnoticable, but as another pointed out, for most people it's not worth it. There are fuel economy gains, but not enough to offset the increased cost of fuel. There are torque gains in the mid-range that you absolutely can feel, and have been verified by dyno. Is that enough to pay the difference in fuel cost? Only you can decide. Agreed that 93 does not improve engine longevity. Higher octane allows the engine to run a more aggressive map (timing) without degrading longevity. That is the important part.

I appreciate your informative post. Would you be able to be more specific with the torque gains running premium?

Out of curiousity, which octane do you choose to run in your personal 5.0?

Thanks!

 

[mada808]

Have you calculated dollar per mile instead of dollar per tank?

No difference in my trial run...

 

[BmacIL]

I appreciate your informative post. Would you be able to be more specific with the torque gains running premium?

Out of curiousity, which octane do you choose to run in your personal 5.0?

Thanks!

I will dig up a dyno chart showing the gains...it's not small (~20 hp/lb-ft). I'm running 93 now because it's been fun and I've done some spirited driving. In the winter I was running 87 because you can't really use it much anyway, and cheaper. 93 is still cheap enough right now that it doesn't hurt, but if it went up another $0.50/gal I'd probably reconsider. That stuff starts to add up when you're only averaging 19 mpg on your commute.

 

[Hack]

They're not unnoticable, but as another pointed out, for most people it's not worth it. There are fuel economy gains, but not enough to offset the increased cost of fuel. There are torque gains in the mid-range that you absolutely can feel, and have been verified by dyno. Is that enough to pay the difference in fuel cost? Only you can decide. Agreed that 93 does not improve engine longevity. Higher octane allows the engine to run a more aggressive map (timing) without degrading longevity. That is the important part.

Fuel economy gains with 93 octane? Only if higher octane gasoline is used to increase the octane. If the octane is increased by adding a higher percentage of ethanol to the fuel your fuel economy will decrease with higher octane fuel.

Your butt dyno must be more sensitive than mine. I couldn't tell the difference between 87 and 91 in my GTs I've owned. But then again it's usually cool enough here that the timing probably isn't retarded with 87. On a hot afternoon in bumper to bumper traffic the timing might be retarded, but I won't notice, since I'm stuck in traffic.

 

[jasonstang]

No difference in my trial run...

Like no better gas millage?
Or costs the same to run?

 

[BmacIL]

Fuel economy gains with 93 octane? Only if higher octane gasoline is used to increase the octane. If the octane is increased by adding a higher percentage of ethanol to the fuel your fuel economy will decrease with higher octane fuel.

Your butt dyno must be more sensitive than mine. I couldn't tell the difference between 87 and 91 in my GTs I've owned. But then again it's usually cool enough here that the timing probably isn't retarded with 87. On a hot afternoon in bumper to bumper traffic the timing might be retarded, but I won't notice, since I'm stuck in traffic.

Like I said, I only noticed a butt dyno difference since it's been warm out. I probably keep the engine in speeds closer to lugging than some people do when accelerating, where you'll notice it more.

On fuel economy, I'd have to find out from people I know in calibration, but I can only think that the increase in octane allows for a small spark advance, so acceleration while cruising (6th gear, 2000 rpm) is more efficient. It's small (~3%), but I had about 20 trips back and forth between Chicago and Detroit last year to collect data on it.

 

[KevinG]

89 octane. Not the lowest, nor the highest - its just right in the center...

 

[Azzurro]

87 Only.... Why pay more???

 

[RNstanger]

87

 

[CEHollier]

I run ETOH. MPG sucks but it's cheaper than 87. Performance is definitely better than 93.

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