Premium Fuel

[frdfrst]

sounds like a case of wrong person in a good car.like if you have to ask the price you don't belong.

 

[gashog]

Wow... tough crowd.

 

[KaPPaBaLL]

I just ran into the same situation. Apparently the gas station pump accounts for fuel density (changes in volume due to temperature) while the on-board computer only accounts for fuel flow.

that's why i always buy gas at night. when it's cooler and dense. plus using the fuel pump on the "low flow" notch on the nozzle gets you more fuel than "high flow" notch; less air to be sucked in and registered as fuel... there is a write up on it. I'll try to find it later...

 

[Mr_Q]

Guys in the end you are talking about 30cents difference between reliable, clean burning, power adding fuel, and peace of mind.

Give
Me
A
Break

Buy 91 (or 93)

 

[metroplex]

91/93 octane doesn't burn as cleanly as 87 octane.

 

[Mr_Q]

By cleaner I meant more efficient and motor safe, which it is. But given the amount of fuel additives in most high octane deliveries, it IS a clean burning fuel. As far the internal motor parts are concerned.

And as most know by the time the fuel hits the combustion chamber taking in to account density and tempurture....91 becomes a couple points lower in it's actual octane rating as does 87.

So the higher the better.

 

[o0Dan0o]

that's why i always buy gas at night. when it's cooler and dense. plus using the fuel pump on the "low flow" notch on the nozzle gets you more fuel than "high flow" notch; less air to be sucked in and registered as fuel... there is a write up on it. I'll try to find it later...

This is the second time I've seen that, and I can tell you that the change in density of gasoline from a ~20 degree change in temperature is going to be insignificant. Not to mention the tanks are normally underground and will only see a nominal change in temp.

The pump speed I doubt, but it's possible and I have nothing to contradict it.
Dan

 

[KaPPaBaLL]

just something i read about, and started doing. no hard evidence in it being factual or not.

 

[o0Dan0o]

No offense meant, just trying to squash a rumor for everyone's sake.
Dan

 

[KaPPaBaLL]

i know

 

[metroplex]

By cleaner I meant more efficient and motor safe, which it is. But given the amount of fuel additives in most high octane deliveries, it IS a clean burning fuel. As far the internal motor parts are concerned.

And as most know by the time the fuel hits the combustion chamber taking in to account density and tempurture....91 becomes a couple points lower in it's actual octane rating as does 87.

So the higher the better.

It might seem odd that fuels with higher octane ratings explode less easily, yet are popularly thought of as more powerful. The misunderstanding is caused by confusing the ability of the fuel to resist compression detonation as opposed to the ability of the fuel to burn (combustion).

Thus it is possible to formulate high octane fuels that carry less energy per liter than lower octane fuels. This is certainly true of ethanol blend fuels (gasohol), however fuels with no ethanol and indeed no oxygen are also possible.

Alcohol fuels such as methanol and ethanol, are partially oxidized fuels and need to be run at much richer mixtures than gasoline. As a consequence, the total volume of fuel burned per cycle counterbalances the lower energy per unit volume, and the net energy released per cycle is higher. If gasoline is run at its preferred maximum power air/fuel mixture of 12.5:1, it will release approximately 20 MJ (about 19,000 BTU) of energy, where ethanol run at its preferred maximum power mixture of 6.5:1 will liberate approximately 25.7 MJ (24,400 BTU), and methanol at a 4.5:1 AFR liberates about 29.1 MJ (27,650 BTU).[citation needed] To account for these differences, a measure called the fuel's specific energy is sometimes used

http://en.wikipedia.org/wiki/Octane_rating

Since the S197 GT was engineered to run on 87 octane, you're not getting any more power using 93 octane unless there are some problems with the powertrain/fuel delivery (hotspots, clogged injectors, etc...)

 

[JimsWhiteGT]

You can also void the warranty by not using the recommened octane.

 

[The Fang]

I have been curious, does anybody buy 89?

 

[DarkFireGT]

I always bought '89 before my tune. 89 is cheaper than 87 here because it has a bit of ethanol in it. But now they're both tuned for 93.

 

[1hOtStAnG]

The best advice is to always run the lowest octane recommended for your car by the manufacturer; in your case, that's premium fuel. In the case of a Shelby GT one has to wonder why you'd spend 35 large on a vehicle then try to save pocket change by using lower octane. How much will you save? Someone can check my math, but in my area premium is $0.20/gallon more than regular. If you get 18 MPG overall (not unreasonable) and drive 12,000 miles a year you'll save a whole $133 each year by burning regular. Not worth it to me--you make up your own mind.

That's what I was thinking.

Also, as a point of interest since we're talking fuel here. I live in Denver, CO and I use 91 octane with a 93 performance tune on a CL7140 from Diablosport. I also have the C&L "street" CAI.

Anyways, I am to do this because the air is so damn thin up here. Colorado is not a very good place for go fast cars.

 

[RottenRonny]

91/93 octane doesn't burn as cleanly as 87 octane.

He's talking about a Shelby GT that comes from the factory with a 91 tune.

For a regular GT, 87 is the way to go, but for the Shelby, you're better off putting the premium in.

 

[mustangfan1990]

93 is more combustible and last longer. NO SUBSTITUTE. If it wasnt better Ford wouldnt tell you to do it

 

[metroplex]

93 is more combustible and last longer. NO SUBSTITUTE. If it wasnt better Ford wouldnt tell you to do it

93 octane is more knock resistant than 87 octane.

 

[sonnier]

I typically use 87 but sometimes it just runs like poo, maybe bad gas or the ethanol in it or something but when that happens I mix in 89 and everything is fine. When I do track events I go with 89 to prevent detonation since I'm running higher temps and putting more stress on things. I plan to get a tuner soon, though to run 93.

 

[GOLDENPONY]

GAS

Sell the Shelby - Buy a Focus.