Gas Grade...

[Temple]

At .30 a difference between a gallon of premium and a gallon of regular, I figure it costs me less than two and a half cents per mile to really enjoy driving my truck. I know that all adds up but I did try the 87 economy and the 87 performance tunes. While the economy tune gave me another mpg and the 87 performance was tolerable, the true bang for the buck came when kicking it down while running 93. The savings was negligible while the performance gains are significant.

 

[AZEngineer]

I think the quality if gas is very regionally dependent. Here in the Phoenix area all gas comes from one single pipeline from Tucson to Phoenix. I'm told that once it arrives here each brand adds their own additives. Supposedly they add octane booster too. Here we can only get 87, 89, and 91 octane.

When I had a BMW the service writer told me that BMW, Mercedes, etc etc had worked together to drive a higher additive standard. The collective has a list of the best brands here. Top Tier Gasoline

Costco locally here now advertises that they have top additives.

In the first few tanks I tried 87 and 91 and didn't see a difference. We uses to only use Shell but now we are using costco too.

 

[Cleave]

I'm amazed 76 is on that list

 

[Icecobra]

Octane has nothing to do with horsepower or mileage. Its a breaking down of crude oil that makes octane rated fuel.. It is made in to gasoline to prevent pre-ignition (knock) of the fuel. The octane the less control of the ignition timing and so under compression it explodes at less than the most efficient moment. In the motors in our trucks using the higher than 87 only results in you spending more money at the pump for an additive your truck can not take advantage of. We have knock sensors in the engine and computers to prevent knock. Our engines are designed with less compression than ideal for proper burning of fuel. This is how Ford gets around people using cheaper fuels in the trucks and cars. This is not new science and it is as old as combustion engines. The logic behind octane has been based on the ability to cause the ignition at exactly the right moment of the stroke of the piston to get maximum explosion in the combustion chamber to yield maximum BTU from the fuel. In most places all fuel has to meet a certain standard that Ford uses to determine minimum fuel requirements. Tier one fuel such as Shell, Chevron, Texaco use additives after the fuel comes from the refinery. If these additives actually do anything no one really knows but you can not prove they don't do as advertised so it gets added... Tier two stations like circle K mom and pop shops etc. usually have no additives so if you think you need them then only use tier one stations. Back to octane and additives, if you have clear fuel no additives you would get more MPG from fuel. But because corn producing states rely on us using ethanol those congress people push for ethanol use. It yields less BTU then regular gasoline and you have to burn it at a 1.5 margin to gasoline to get the same results. This one reason fuel economy drops when you add ethanol. Ethanol also causes damage to everything it comes in contact with but that's another story. Now in California if you want to see your fuel economy go up find a local boat launch that dispense fuel. Almost all boat fueling stations are ethanol free because it absorbs water. You don't want fuel next to or in boats that are on the water that absorbs water... makes sense.. So go fuel up at the boat dock, fuel costs more if its ethanol free... Drive a couple tanks of that in your truck and you will see a difference in the performance because its ethanol free..... So much for your science lesson today... Tomorrow why we owe so much to the dinosaur...

 

[Cleave]

Octane is not an additive, it the measure of the volatility of fuel, and how fast that fuel burns, the reason lower octane fuels sometimes will cause knock is because they burn faster, which instead of pushing the piston down the cylinder it hits it and causes rod knock or piston slap, or the fuel lights off due to compression before the spark plug fires, which causes two flame fronts to collide inside the cylinder, dramatically increasing the pressure and heat inside the cylinder and causing damage to the engine, running higher octane fuel is better on the engine because it will produce the same or more power over a longer period of time, reducing the stress on internal engine components, granted ethanol supplemented fuels can cause similar damage to the piston and injectors due to the corrosiveness of the ethanol (although it takes much longer than running low octane fuels)

 

[nohel]

Thanks cobra i'm glad some one could put what i was thinking in to words. I wish you would of went in to compression ratios and knock with the raptor, being on the low side of 9.8 to 1 or so it doesn't really require a higher grade fuel to prevent detonation. Some one needs to dyno a stock one with 87 and 93 i think the difference would be less than 4hp at the wheels.

 

[Icecobra]

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

During WWI, it was discovered that you can add a chemical called tetraethyl lead (TEL) to gasoline and significantly improve its octane rating above the octane/heptane combination. Cheaper grades of gasoline could be made usable by adding TEL. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:
•Lead clogs a catalytic converter and renders it inoperable within minutes.
•The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).

When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline (known as AvGas), and octane ratings of 100 or more are commonly used in super-high-performance piston airplane engines. In the case of AvGas, 100 is the gasoline's performance rating, not the percentage of actual octane in the gas. The addition of TEL boosts the compression level of the gasoline -- it doesn't add more octane.

Currently engineers are trying to develop airplane engines that can use unleaded gasoline. Jet engines burn kerosene, by the way.

 

[Cleave]

I'm just saying that just because you don't need to run 91 or higher octane in your vehicle doesn't mean it wouldn't run better with it, the facts are that it will, 87 octane produces nearly the same amount of power as 91 octane in a shorter period of time, run a car into a wall with a sustained 5,000 lbs of force at 10 miles per hour, then run another car into a wall with a sustained 5,000 lbs of force at 20 miles per hour, the 10 mph car would represent running 91 octane and the 20 mph car would represent running 87 octane, they both would sustain damage (which would represent wear), but the 20 mph car would sustain much more damage

 

[Icecobra]

Will one gallon of 87 run any better or provide more performance in the stock setup .. NO!.. In order to get more from 91 or 93 you have to adjust timing in the computer. Can it be done yes, but Ford in stock computer system will not adjust timing to take advantage of 91 or 93 over 87 octane fuel...

 

[Cleave]

The stock computer can do a lot more than everyone gives it credit for, unless you're doing something major like adding a supercharger or changing the entire intake system to velocity stacks or the exhaust system to headers, the computer will compensate and run just as well as if on a properly done tune, although it will take time for it to learn it and it will have more flexibility, the pcm will use the knock sensors and air fuel ratio sensors to determine what fuel the engine is running, every once in a while every engine out there running a stock pcm will run the engine timing advance up until the engine starts to misfire, using this against a table of values it will determine what octane it is running, or the equivalent based on quality of gas, this means that even though you're running 87 octane, if it's poor quality gas, the engine timing can be retarded to the point of running 85 octane or less to protect the engine, the pcm will usually also run the timing up after a fill up if you put in enough gas for it to realize a fill up has occurred to determine if a different grade gas was put in it