Who uses 87 octane with stock tune on the 5.0?

SkyRender · Feb 13, 2011

I was just wondering who all runs 87 octane in their 5.0s that haven't been computer tuned. How much of a performance difference do you notice between 87 and 91?

Sparty92 · Feb 14, 2011

SkyRender said:
I was just wondering who all runs 87 octane in their 5.0s that haven't been computer tuned. How much of a performance difference do you notice between 87 and 91?

My car came with a tank of 87. After that tank was done, I put in 93 octane. I haven't gone below that since then (2,000 miles later). I couldn't really "drive" the car because of the cold/snowy weather, so I can't comment on performance improvements.

I know the computer adjusts for octane and the "rated" hp/tq is with 93 octane I believe.

I do have a SCT tuner and tunes sitting in my email for 87 street, 91 performance and 93 race....from AM/Bama. When Spring gets here I will try them all, but the plan was only to use 87 if the price of gas gets to be annoying...or maybe just for winter use.

For a stock car, I wouldn't run 87, but that's just me. I think having a "tune" for 87 will allow it to run the best it can on that octane, so that's why I ordered it as part of my package.

SkyRender · Feb 14, 2011

I just picked up my car tonight. It has a full tank of 87 octane. I'm going to fill it up with 93 when it gets to about 1/4 tank. I'm curious as to how much of a difference it will make. Unfortunately, it was dark, raining, and rush hour when I left the dealer tonight, so I didn't get a chance to get a good baseline...yet.

The rated HP numbers are for 91 octane from the factory.

Sparty92 · Feb 15, 2011

SkyRender said:
I just picked up my car tonight. It has a full tank of 87 octane. I'm going to fill it up with 93 when it gets to about 1/4 tank. I'm curious as to how much of a difference it will make. Unfortunately, it was dark, raining, and rush hour when I left the dealer tonight, so I didn't get a chance to get a good baseline...yet.

The rated HP numbers are for 91 octane from the factory.

Are you gonna beat on the car to get your "baseline"? It's a brand new car, too! I can't imagine there'd be much going on for the butt dyno between 87 and 91 octane. Perhaps a 93 with tune will give you something to can "feel."

I will find out soon, as I have 3 tunes sitting in my email. I need to try to find a Pee Cee to update my tuner and DL my tunes to the tuner. I wanna beat on the car a little while it's stock to see where I'm at, then upload a tune.

I'm not sure if I wanna start out with 87, then go to 91 and then to 93? Or just go straight to 93. Hmmm..

SkyRender · Feb 15, 2011

I only got 400 miles on my pony. I'm sure as heck not going to beat on it.

Although occasional bouts of full-throttle acceleration helps seat piston rings.

642mx · Feb 27, 2011

My dealer told me the 5.0L will make right at 400 horse with 87 octane and 412 horse with high octane. They said I can run either of them... I'm going to stick with the cheap stuff since I doubt I can feel (or need) and extra 10 horse on the street.

My car has 500 miles on it now and seems to run fine on the cheap stuff.

Rhymhoont · Feb 27, 2011

That's actually a good question. On older engines, lower octane gas is actually better unless it starts knocking. But the new 5.0 is 11:1 which in old calcs would mean you needed at least 90 to have any good advance on your timing. With good advance you would need 102.

So you add in the voodoo with all the cam timing tricks and well, who knows. I live in a Cali and even the premium 92 is crap and that changes from summer to winter. My 66 mustang hates all cali gas unless I knock it down a few degrees.

Since my GT is on order, I want to know this one. And how often I should drive to NV for a load of "good" gas...

Coyote5.0 · Feb 28, 2011

There is a station in my town that sells 89 octane for the same price as 87, so I used that last fall. It seems to run great on it.

When I get it out this spring, I'll probably switch to premium, since I found out that the premium at many of the stations around me doesn't have ethanol in it. I'll actually be breaking even price wise with the fuel mileage difference.

SkyRender · Feb 28, 2011

I did not notice any difference in switching from 87 octane to 92 octane while driving on the street. Apparently that 12-horsepower difference is either too small to be noticed or only happens at high RPMs not encountered on the street.

That being said, I run 92 or 93 octane anyway because of the motor's high compression and the fact that it's only 20 cents more expensive per gallon around here.

Also, if you have put a computer tune on your engine, you will have to run a higher octane.

Sparty92 · Feb 28, 2011

SkyRender said:
I did not notice any difference in switching from 87 octane to 92 octane while driving on the street. Apparently that 12-horsepower difference is either too small to be noticed or only happens at high RPMs not encountered on the street.

That being said, I run 92 or 93 octane anyway because of the motor's high compression and the fact that it's only 20 cents more expensive per gallon around here.

Also, if you have put a computer tune on your engine, you will have to run a higher octane.

Exactly. Twenty cents/gallon more @ 10 gallons at a top off is only $2.00 more per tank. If you can't swing that, you need to stop eating.

Regarding the computer tune and needed higher octane...you can get tunes for 87+ octane. I have 87, 91, 93 Octanes....yet to be uploaded, but I have them.

Who uses 87 octane with stock tune on the 5.0?

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