I was just wondering what most of you are putting in their tank (besides the tiger!)... In order to get maximum performance out of my new 5.0, I was planning to start right away with 93 octane fuel. One of my first mods on the list will be a Steeda CAI and tune anyways, so might as well go for it.

What are your thoughts and experiences?

 

So far I have been using regular on trips where I am just highway cruising, and the rest of the time mostly premium.

 

even without a tune in my 2010, I used premium. And now that I'm tuned for it, it's the only way!

 

no 93 in so cal so 91 pour moi

 

93 every time.

Theres actually a spot near me that sells 100 octane with no ethanol. I wonder if this engine would make use of it.

 

I put 93 in mine.

 

Not the octane... but the lack of ethanol will increase performance. Octane is only a measure of resistance to pre-ignition and detonation (knocking). Higher octane gas is not better gas and using a higher octane than specified is just a waste of money (all other things being equal).

As with many modern computer controlled engines, the 5.0 has an optimum octane requirement (91 R+M/2) but can be run at lower octane levels. The computer compensates by retarding timing to prevent knocking but that also reduces performance. However, going to a higher octane than 91 will not improve performance.

OTOH, gasohol has less potential energy (by volume) than straight gasoline. So that "racing" 100 octane gas will likely give you better performance... not because it is 100 octane but because it has no ethanol. And the difference can be quite significant. When stations around here first started to switch to ethanol, I could feel a noticeable seat-of-the-pants performance difference when I filled up with gas compared to gasohol. Whether it's worth the added cost is an individual decision.

 

can anyone make you a 100 octane tune?

 

There is no 91 in MA so ive been using 93. I believe Sunoco has something higher around here but im not confident

 

Yes.

I'm running 93 octane in my V-6 because i have a tune being made for it.

 

I made the dealer give me the money and let me go fill it up to make sure it didnt get 87.

Phillips 66 Premium 93 currently. Its the only source of Top Tier rated G100 (No Ethanol) locally.

 

Question for you. Good read so would you be better off using 87 octane no ethanol or 93 octane with 10% ethanol when it comes to performance?

 

93, baby!

 

94 here at Petro-Canada with a Steeda CAI & 93 tune.

 

I will say this. I have tried 4 different types of gas 3 were 91 octane with 10% ethanol from shell bp and whatever qt gas is then I found a phillips 66 that had 93 10% and have drove two tanks of that. It might be in my head but ill go back for that gas again for sure.

 

Good question. You highlight a common misconception that octane has a relationship to power produced - it doesn't, at least not directly.

A gallon of 87 octane gasoline has exactly the same energy potential as a gallon of 93 octane gasoline - about 116,000 BTU. Ethanol has higher octane but lower energy potential. Pure ethanol has an octane rating of about 113 but only about 76,000 BTU of energy potential. That's why your performance (and mileage) suffer when using an ethanol blend. A gallon of E10 (10% ethanol) has only about 112,000 BTU.

So, all other things being equal, a gallon of pure gasoline (regardless of octane) will give you more performance than a gallon of an ethanol blend. The problem is... all other things are not equal. The computer will advance the timing with higher octane fuel to improve performance. I don't have numbers to quantify the difference between power produced with retarded timing for low octane fuel and power produced with advanced timing for higher octane fuel. My personal experience has been that retarding the timing to prevent knock has a bigger impact on performance than using an ethanol blend.

When gas reached $4 per gallon I tried switching from premium to midgrade to save 10 cents per gallon (knowing that the computer would compensate). That 3% drop in octane caused more than a 10% drop in gas mileage and probably about the same drop in performance. In the end, you should see better performance using the 93 octane ethanol blend than the 87 octane pure gas because the higher octane allows the computer to increase timing without risking knocking.

(This doesn't apply to the V6 engine which gains nothing by running higher octane.)

 

93 here, doesn't bother me to use it.. my 03 gt had to have it because of the cams/timing

 

Anyone know where you can find no-ethanol gas in central Massachusetts, northern Rhode Island, or north-eastern Connecticut?

I'm guessing they made it illegal, but just checking.

 

Same here in Florida... won't find anything but ethanol-blend gas.

 

Yup, initially the E10 was promoted by the government by giving a five cent per gallon tax rebate but now it has become law. Starting 12/31/10, it will be illegal in Florida to sell gas unless it contains 9-10% ethanol. There are exceptions for aircraft, watercraft, collectible cars, off-road, motorcycles, and small engines (lawnmowers, generators, etc.). At this point the question is moot since there are no terminals in Florida storing pure gas anymore - stations would have to truck in from out of state if they wanted it.