The esso I worked at only had 2 kinds of fuels.
Regular (87) and Premium (91)
the Extra (89) was actually a half and half mix coming out of the 2 tanks.

 

The Mustang's 4.6 engine is not a "low" compression motor. But to put this whole, "you're car will run worse with high octane fuel" nonsense, I put my car to the dyno. I have access to a shop that had heard the same arguments from various sources, so we agreed to use my car as the guinea pig.

For the first 3 pulls, we reflashed the CPU back to stock, re-installed the HC trap and made three pulls on the 93 octane in the tank.

Avg: 258hp

Following these runs, we drained the remainder of the 93 octane. Put in 4 gallons of 87 octane fuel (same brand as the 93) drove the car about 20 miles to be sure the gas in the lines was used and made 3 more pulls. (After a cool down to get the engine temp back to what the original runs were made at) Result:

Avg: 255hp

The car actually made an average of 3 hp less on the suggested rating than with the 93.

 

You didn't happen to reset the computer now did you....

 

3hp is negligible at best, plus there are too many variables to control in such a loose environment (i am aware that you took efforts, but there is more to it). Im sure Ford knows what theyre talking about, no need to get higher octane stuff unless you higher your compression ratio or use forced induction.

 

The only car I've ever owned that ran better on premium was my '95 Taurus SHO and it was designated by Ford "Premium Recommended". It would run on regular but you could feel the difference with premium in the tank.

 

What were your actual pulls on each of those runs, not just the average?

 

Really! You've become Atilla the PUN!

 

To elaborate on my previous reply I have no scientific reasoning behind using super. Even though I am quite aware Ford recommends 87 I guess in my mind I just feel that 93 is "better" for the car. When I actually get to drive it which is not as often as I would like I prefer to treat her good so I dump in the 93. I am going to have to use 93 anyway when I start seriously modding her so why not use it now. The couple dollars extra I pay doesnt make a difference anyway.

 

Really! You've become Atilla the PUN! [/b][/quote]
Sometimes it's Good to act FUELISH! Talking about OCTANE can be Quite a BOOST! Especially if you Get TANKED first! Well I Think I have Had My FILL of Puns for the day! Man I got a Lot of MILEAGE of that Poll!

 

I agree, there are way too many variables to account for.

Our test was to see if we LOST hp by using a higher rated fuel, not if there was any GAIN to be found. I never doubted that there was anything to gain by running a higher octane fuel, rather, I just had doubts that running 93 on the stock tune would make the car run worse, as it has been put forth in this very thread. I chalk the hp difference not to the 93 octane fuel but to some variable we did not take into account or that was different between the pulls.

I have no doubt you don't NEED higher octane fuel, but running it is not going to hurt you performance-wise.

 

Lower octane gaslines ignite faster (more easily). High octane gasolines ignite slower (less easily).

Why do we need that?

Because octane rating help us determine how fuel combusts *under pressure*. We want fuel-air mix to ignite with the spark, and not because it gets compressed and heats up. Compression ignition means pre-ignition. This causes the dreaded pinging noises, and potential damage to cylinders and valves, since the fuel-air mix is "going off" at the wrong instant.

Higher compression engines need higher octane to help hold back pre-ignition, which would be more likely with their higher compression ratios.

That's why, on modern engines, if your EGR valve and/or EGR solenoid is not working properly and your engine is making a racket, you can "appear" to eliminate the problem by going to a higher grade of gasline, which resists compression ignition, and helps eliminate the knocking and pinging. But the real problem is (probably) the EGR valve or solenoid.

Running slower igniting (higher octane) fuel in your 87 octane-rated Mustang GT means it is probably not burning that fuel efficiently, because the engine is designed to efficiently burn 87. So you are receiving no performance gain, possibly taking a performance hit, and certainly taking a hit in unburned hydrocarbons from the incomplete burn of the high octane (slower igniting) gas in the engine cycle.

 

That's funny the HC level on my car when emission tested with 93 octane actaully read LOWER than it did when it was tested on 87 octane when I purchased it.

 

that was the greatest pun ever... kudos friend

 

Seen a ton of debate over gasoline grades. The general conclusion to people who have tested, dynoed ect have found cars run pretty much the same no matter the octane unless it has greater than 10:1 compression, then sometimes there would be knocking with lower grade fuel.

The car "has been tuned to run on 87" means only that you can run 87 without the ping/knocking, not that they were only able to extract optimum performance from 87. You certainly wont lose performance running 91. It's an added bennifit that it can run on 87 but not a necesity.

 

No FUELIN I appreciate that. I was starting to feel a little EMPTY that my Humor was not appreciated thanks for the ego FILL! Got to go Elvis is on the Radio singing TREAT ME LIKE A FUEL! B)

KC

 

Wow! I would never have guessed how many different opinions this poll would get!


KC

 

I guess the companies selling Octane Booster are sol as far as the 05 Stang!

KC

 

Anymore Fuelish questions?

 

Yes indeed, it is a very Volitile subject

 

So much good and bad info...

1) Unless you get a flash, you are wasting your money. The car will run the same on reg, mid or premium. period...

2) Most people do not know this, but gas loses octane when it sits for long periods of time. Since regular fuel sells faster, it is usually "Fresh" gas and is usually close to the octane rating. Premium however, is sold at a much lower rate and may set in the tank for many weeks/months before you buy it. "Old" premium may not be much if any higher octane than "fresh" regular.

3) Almost all gas in a given area comes from the same bulk storage units. To get the best price and the "freshest fuel", you should buy your gas at a low cost/high volume dealer.

4) Never buy gas at a station if you see a fuel truck there or just leaving. All tanks are required to have a certian amount of water in the bottom of the tanks to prevent gas from seeping out of the tank if it is leaking as the gas will float on the water. The fuel dump stirrs up the water and the trash...