MusiccityGT

Here is a clip from a Powerpoint presentation that I put together as a training video foe ERS drivers that work under me.

Gasoline is a complex blend of carbon and hydrogen compounds. Additives are then added to improve performance. All gasoline is basically the same, but no two blends are identical. The two most important features of gasoline are volatility and resistance to knock (octane). Volatility is a measurement of how easily the fuel vaporizes. If the gasoline does not vaporize completely, it will not burn properly (liquid fuel will not burn).
If the gasoline vaporizes too easily the mixture will be too lean to burn properly. Since high temperatures increase volatility, it is desirable to have a low volatility fuel for warm temperatures and a high volatility fuel for cold weather. The blends will be different for summer and winter fuels. Vapor lock which was a persistent problem years ago, exists very rarely today. In today's cars the fuel is constantly circulating from the tank, through the system and back to the tank. The fuel does not stay still long enough to get so hot that it begins to vaporize. Resistance to knock or octane is simply the temperature the gas will burn at. Higher octane fuel requires a higher temperature to burn. As compression ratio or pressure increases so does the need for higher octane fuel. Most engines today are low compression engines therefore requiring a lower octane fuel (87). Any higher octane than required is just wasting money. Other factors that affect the octane requirements of the engine are: air/fuel ratio, ignition timing, engine temperature, and carbon build up in the cylinder. Many automobile manufacturers have installed exhaust gas recirculation systems to reduce cylinder chamber temperature. If these systems are not working properly, the car will have a tendency to knock.

But then again, I don't know much about engines or fuels.

93BlackNotch

You just agreed with what I said...LMAO...

"Most engines today are low compression engines therefore requiring a lower octane fuel (87). Any higher octane than required is just wasting money."

MusiccityGT

Oh yea, I was not disagreeing with all you said. Indeed for a bone stock car, 87 is fine, 89 works and 93 is a total waste of money. But, with mods and tunes you have to be aware of potential damage from detonation. In my case I have to use 93 because of timing advance and A/R settings. But to think that a well performing, properly tuned stang is faster with 87 than with 89, I question that. Indeed it may provide a slighly faster burn, but a noticeable power gain? I am glad I provided you with some humor to top off your evening. [8D]

93BlackNotch

Hahahahaha, it's all good.... You occupied a few minutes of my precious internet time....lol

algregory

I have an '05 GT in the SF Bay Area of California. I used to be a believer in premium in everything. Finally read enough material to understand if the Mfg. recommends an octane, that is the one to use. Even read of instanced of stubborn premium users finding out their rides worked better on regular afterall.

I've been to "Tech" sessions put on by Chevron Oil, I believe the additives are good across the grades. Found out why it is good for engines and drive trains that unleaded became the common fuel.

I use Redline Fuel Cleaner on a regular basis. My old BMW with 260k miles on it has, from the factory, see through fuel lines. I had to replace one due to abrasion, the rest are original. You can still see through my fuel lines, I've seen others that were no longer see through.

5StangsandCounting

87 octane works just fine in stock stangs... With a few upgrades and a more aggressive tune, it's a different story.
I used to be able to get some knocking with hard acceleration at low rpm (5th gear at low speeds) in my 03 stang, but the new gt's don't seem to have this problem. I have tried different grades, and can't see any difference in stock form. Save the extra gas money while you can...

Stooge

In a stock motor, 87 octane is the design point. Higher octane fuels will only drain your wallet. The only saving grace is that some higher octane fuels CLAIM to have better additive packages, but this is HIGHLY dependant on the distributor.

Note also that higher octane fuels do burn slower and cooler (is that what you want?), and tend to deposit carbon on the piston tops (due to cooler combustion temperatures). This has a tendency to INCREASE compression over time, and thus the need for higher octane fuels increase. Kinda like an addiction.

Note that higher octane gas is the profit maker for the oil companies. They cost less than a penny more to make and dose, but the gas stations charge 20 cents or more per gallon. Also note that most mid-grade gases (89 octane) is a crude blend of alittle 91/93 octane and alot of 87 - a real inexact science and rarely tested and confirmed.

Our V8's, in stock form, are really mild. No big HP output from the 4.6 liters. Low compression, mild cams with smooth idles. Don't be fooled to use the higher octane fuels unless cost is no object.

viking396

Did I say use 116?? Did I say use 93 every few months? Nope and uhhhh nope. I also didn't say running higher was necessary, I said I did it because running 87 CAN cause problems so I use higher to be safer. The difference between how 87 burns vs 89 is much different than 116. I always use the same fuel, it's just never 87.

The only time you use crap low octane fuel is when you are in high altitudes, the requirement for octane goes down as you go up. Running 87 means that at times you could be running lower, I refuse to put my engine at that risk and I also know that buying 93 means sometimes I'll get a bit lower because the gas companies don't give a crap and because some dealers buy cheap and sell it as higher...

viking396

Good points all, however as I said, many times what you dump down the tube is actually lower than 87 and while I don't tout putting in 93 into a stocker, I feel that 89 gives you elbow room to safely floor it without the worry of detonation. I have seen too many times where people are driving in the summer and it's 100f and everything around me is pinging. Now I have very sensitive ears so I know I hear somethings others can't and the ping seems to me much worse on GM cars so, I use 89 and feel safe doing so, even if it costs a bit more.

Sorry for the rant but hearing people say the Mfg says it's ok, the gas companies say it's ok so just do it drives me nuts, since when did we suddenly believe them for this when we don't for simpler things?

MikeVistaBlue06

That is not exactly the case. First of all, most of the gasoline in a specific area comes from one or two sources. Most big cities will have 1 or 2 tank farms that all of the major brands use. They then add their specific additives and call it "Texaco" "Shell" "Exxon" etc. Chevron advertisements claim all of their gasolines have Techron in them. If you need fuel injector cleaner, I recommend Techron purchased at Walmart or an Autoparts place--it has Naptha and Stoddard solvent in it to clean the injectors.

I have used regular 87 in all of my cars since 1986 with no issues at all.

The rule of thumb is if a car knocks on 87, use 89, if it knocks on 89 use 91, if it knocks on 91 use 93. If it knocks on 93 you're probably SOL and need to get the car checked out! Buying more octane than you need is just a waste of money.

One fact many don't know is that 87 octane fuel has more energy in it per gallon than 93; a higher octane number means less energy and that the fuel burns slower.

Finally, there are a number of things that go into whether or not a car will run properly on a given fuel. I have a 1997 Dodge Dakota 5.2L V8 truck. I had the computer flashed on it with a hot tune. With the stock ignition and Champion plugs, I had to run 93 or it would knock. However, changing the plugs to a cooler Autolite version and adding an MSD ignition system (coil, 6AL box, and spiral wound copper wires) and a HD rotor and cap, I can now run 87 octane with that hot tune and it doesn't knock! The plugs show a perfect burn pattern on them too (insulators are still white and there is a slight white/grey coating on the plug. Also, I pulled the intake one day to check a bellypan gasket, and the injectors are clean--no residue on them what-so-ever, and this is after 50,000+ miles of 87 octane, the majority of which I purchase now from either Sam's or one of the grocery stores (Tom Thumb or Kroger).

I also ran 87 in Bluebonnet until I added the tune and goodies. Now she gets 93.

Hope this helps.

Mike