I don’t know if this is just me, so I thought I’d ask. It is my understanding that the new 5.0’s are at “full power” on 91 octane, and will automatically adjust to whatever octane is being used. The gas stations I typically use (nearest to me) do not carry 91 octane, so I’ve been running 93 instead.

A couple weeks ago, I happen to fuel up at a gas station, that is a bit out of the way, that does carry 91 octane, and there seemed to be a noticeable INCREASE in torque and power. I could really feel it (or so it seemed) in the lower rpms.

Well, after fueling up with a couple tanks of 91, I got stuck filling up with 93 again yesterday. And it seems to have lost a little something as a result. Is this all in my head? I could see there being a difference if I was using a lesser octane than 91, but not a higher octane. Any input would be greatly appreciated.

 

im not sure since i have 93 octane here, but i think that my 91 bama performance tune feels better than the 91 race and 93 race tunes even when using 93 octane.


my advice would be to get a bama 91 tune, totally worth it.

 

Could be gas quality. A station by my parents (in the "country") is ethanol free. Gas by me has ethanol. I get better mpg and car feels stronger with their gas.

 

Higher octanes should not have a negative affect on a tune. But you should be aware that even though your engine can adjust for octane changes, those adjustments are minuscule (single digit RWHP gains at best) in comparison to what a custom tune for a given octane can make (30-40 RWHP gains).

 

It's probably just me then. Maybe I'll try running a lower grade, and if I don't notice much, I'll just save some money and keep running it.

I intend on doing a CAI/tune after this winter. I can't wait. I remember the difference that made in my '07 GT. And, at least I'll get my money's worth out of 93 octane then.

 

I have been getting the 93 octane from the same station this entire time. I'll switch stations next time I fuel up. Great point.

 

There is more chemical energy available in lower octane fuel. It does not surprise me that your car feels stronger with the lower octane. Run a tank of 87 or 89 and you will experience a similar sensation. The problem is that the lower octane fuels are also more volatile and prone to pre-ignition. To get the maximum efficiency out of your motor, you should only run as high an octane as it takes operate without pre-ignition. Any higher and you may not be consuming all of the fuel during combustion.

 

That makes sense. I do notice, when running 93, that there tends to be more of a fuel smell to the exhaust right after I start it up. As if it is running a little rich on 93. It just sucks that it's so hard to find 91 around here.

 

Thanks for all the great feedback. It will only be an issue for another couple months anyway (until the snow starts flying). Then, after I get her out of storage, I'll just do the CAI with a 93 octane tune.

 

Running a higher octane tune than the tune calls for will never rob power.lower quality, regardless of octane raring, will.