What octane do you use

[gtlaw]

I tried 87 for a few tanks and was noticing light spark knock in stop and go traffic when the car was fully up to temp. i switched back to 93 and it completely disappeared

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[Hurricane]

Mine's a DD as well, but has been fed only 93 octane ever since I bought it. Since tuning, I'm definitely married to 93 octane now. Of course, it's readily available all over my area though, so no worries. If for some reason gas goes up to crazy prices again, like $4.50 or $5/gallon for 93, I can easily put a Steeda restrictor tube in my CAI and load the stock tune for a return to 87 octane. I could also just get a new tune from Steeda for 87 as well. Plenty of options are available since the engine itself isn't limited to premium fuel.

 

[QRK]

Virtually every pump here in FL that I've come across only has 87, 89, 93. I've seen 91 just a handful of times so it's always 93 for me.

 

[QRK]

Funny thing, back when I was a broke college kid I drove an '02 Infiniti G35 coupe (6spd of course) and it required premium which was always right around or above $4/gal back then.

As soon as I graduated and got my job at the end of 2014, I bought my Mustang which was right when gas prices started plummeting. It would have been nice if prices dropped before I started making money haha.

 

[Backwoods]

Use shell 91 GT couldn't pass me

 

[Sagacity]

E85 (105+) with Lund tune. Dyno showed about +40hp.

 

[DanielIvan]

91 from Shell. Best we got here on the West Coast for non e85 users.

 

[shahram72]

ok, V6 poser back again... I went back to 87 to see what would happen. So far I notice no drop in mileage, but traffic has been smoother, so that's a factor, but cold idle is a bit rougher. My last car, a 2005 Acura RL I once put 87 in and it was NOT happy. Barely started, rough idle, I thought the car was beefed. A tank of 93 and all was right in the world again.

 

[STANGBOY]

91 but I fill all my cars up with it

 

[Fordever]

91. Highest I can get around here.

 

[jasonstang]

Not my GT but I had a Maxima with VQ35DE engine. I drove it to colorado and used 87 while I was there. My engine sounded like a exhaust leak until I put 91 back in.
10:1 compression ratio with variable timing too.

 

[tcman54]

First 10 tanks I put in was 87 octane, now switched to 93 octane, it feels like a rocket ship to the moon.

Terry

 

[FordTechOne]

Your wasting your money on high octane.

Unless your taking it to the track. Save your money.

Perhaps you don't understand detonation. Detonation occurs when you run low octane/poor quality fuel in a high performance engine. In the best case; it causes causes the engine calibration to reduce performance. Worst case, it causes internal engine damage, which is not something any manufacturer is going to cover under warranty.

Running high octane in a high performance engine is nothing even close to a "waste of money". In fact, it's quite the opposite, as low octane will cause the PCM to pull timing and reduce overall performance. In other words, fuel economy, horsepower, and torque will be reduced, which negates the fuel savings you claim to have from running low octane fuel.

 

[2015 Silver GT]

I only use 87 octane on my car that's tuned for 93. I like living on the edge.

 

[sk8erord]

First 10 tanks I put in was 87 octane, now switched to 93 octane, it feels like a rocket ship to the moon.

Terry

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).

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