Octanes?
Thread Starter
2nd Gear Member
Joined: Nov 2005
Posts: 394
From: Prague, Czech Republic
RE: Octanes?
this will acutally cause the unburned carbon to deposit on the top of the piston. It will also foul out spark plugs.
thx again
I ♥ Acer
Joined: Mar 2006
Posts: 1,278
From: Concord, NC
RE: Octanes?
ORIGINAL: 8cd03gro
i always use 89 because i feel that 87 is a lower quality gas, and 89 is just a little bit more expensive and not too high.
i always use 89 because i feel that 87 is a lower quality gas, and 89 is just a little bit more expensive and not too high.
2nd Gear Member
Joined: Apr 2006
Posts: 308
From:
RE: Octanes?
but hasnt 89 oct with ethanol been shown to cause increased wear over long periods of time? in higher mileaged cars serviced at my bros shop, they've noticed that people who've consistently used 89 octane with ethanol have more problems with seal and pistons. people running 87 in similiar vehicles with matching mileage havent had near the problems. sure, it may burn cleaner, but its a different fuel than just unleaded gas. just wonder if there's any science to match what they've seen.... and now that ive moved to kentucky, there's no longer 91 oct... BOO! now i have to go back to 87 oct tune. only got 81 / 91 tunes...
3rd Gear Member
Joined: Jun 2006
Posts: 515
From: Phoenix, AZ
RE: Octanes?
Wow great thread guys!
I always thought that the higher the octane the better the car would run, here in AZ i have the options of running 87, 89, or 91 octane. I usually run 89, thinking that it's just a step above thus making my car run better, but now I guess I was wrong.
So now i'll be getting 87! Thanks
I always thought that the higher the octane the better the car would run, here in AZ i have the options of running 87, 89, or 91 octane. I usually run 89, thinking that it's just a step above thus making my car run better, but now I guess I was wrong.
So now i'll be getting 87! Thanks
5th Gear Member
Joined: Jun 2005
Posts: 3,319
From:
RE: Octanes?
ORIGINAL: P Zero
The higher the compression the higher octane you NEED. Running too high of an octane with too low compression, the fuel does not completly burn, this will acutally cause the unburned carbon to deposit on the top of the piston. It will also foul out spark plugs. Not to mention your car will run like crap.
-P.
The higher the compression the higher octane you NEED. Running too high of an octane with too low compression, the fuel does not completly burn, this will acutally cause the unburned carbon to deposit on the top of the piston. It will also foul out spark plugs. Not to mention your car will run like crap.
-P.
I ♥ Acer
Joined: Jun 2006
Posts: 675
From:
RE: Octanes?
Well if running a lower octane than what the tune requires will damage the engine, then how does running a lower octane than the manufacturer calls for (vehicles designed to run on higher octane) not damage the engine? What is different between the retuned mustang and the car designed to use high octane fuel?
ORIGINAL: wmtheflash
It's pretty easy...the car is designed from the factory to run on 87 octane. Higher octanes are used for their anti-knock properties, they actually don't burn as readily as regular gas. Burning a higher octane than recommended will produce less horsepower, make the car run worse, cost more money, and will lower your gas mileage.
A reflash to a 91 or 93 octane tune will, amongst other things, advance the timing. Advancing the timing will give you more power, but requires you to use higher octane fuels. The explanation is easy: higher octane gas does not ignite as readily and therefore guards against predetonation (knock) that can cause engine damage.
Using an octane higher than what's required will not damage your engine, but it has no positive benefits in an unmodified car, as explained above. Many vehicles designed to run on premium can safely run on lower octane from the factory (the owners manual will let you know what's safe and what isn't), however, reflashing the computer with a higher octane tune and then running a lower octane gas than required by the tune is entirely UNSAFE. You risk engine damage, then.
To sum it up:
Stock Mustang GT: REGULAR GAS ONLY!
Mustang with SCT or Diablo tune: ONLY USE THE OCTANE THAT IS REQUIRED BY THE TUNE!
It's pretty easy...the car is designed from the factory to run on 87 octane. Higher octanes are used for their anti-knock properties, they actually don't burn as readily as regular gas. Burning a higher octane than recommended will produce less horsepower, make the car run worse, cost more money, and will lower your gas mileage.
A reflash to a 91 or 93 octane tune will, amongst other things, advance the timing. Advancing the timing will give you more power, but requires you to use higher octane fuels. The explanation is easy: higher octane gas does not ignite as readily and therefore guards against predetonation (knock) that can cause engine damage.
Using an octane higher than what's required will not damage your engine, but it has no positive benefits in an unmodified car, as explained above. Many vehicles designed to run on premium can safely run on lower octane from the factory (the owners manual will let you know what's safe and what isn't), however, reflashing the computer with a higher octane tune and then running a lower octane gas than required by the tune is entirely UNSAFE. You risk engine damage, then.
To sum it up:
Stock Mustang GT: REGULAR GAS ONLY!
Mustang with SCT or Diablo tune: ONLY USE THE OCTANE THAT IS REQUIRED BY THE TUNE!
3rd Gear Member
Joined: May 2006
Posts: 700
From:
RE: Octanes?
Sorry, sorry, I forgot! Some folks in the west can actually buy 85 octane gas! By regular gas I meant 87 octane!
Quoting the Mustang GT owner's manual:
Your vehicle is designed to use "Regular" unleaded gasone with pump (R+M)/2 octane rating of 87. We do not recommend the use of gasoine labeled as "Regular" that are sold with octaine ratings of 86 or lower in high altitude areas.
If regular gas in your area is 85 octane, then do not burn it in your Mustang.
Each vehicle is different. Sometimes, running a lower octane won't hurt your engine, it just lowers power and runs rough. You should consult your manufacturer, owners manual, or other trust source before using an octane lower than the recommended octane. For our cars it's pretty easy, 87 octane for stock or if your car has a tune use the octane that your tune requires.
Your car will be it's most efficient, get the most horsepower, and run it's best with the recommened octane, not with a higher octane and certainly not with a lower octane.
That's the great part of Mustang GT's...all that HP on 87 octane! Decent gas mileage, too. Cheap to buy, cheap to fix, cheap to run, cheap to modify, that's the best part of the Mustang (and probably why it will out sell the new Camaro, but that's another thread!).
To answer your question:
Car manufacturers have to overdesign their vehicles for everything. If it takes a higher octane, then they know that some person will make a mistake and put 87 octane in it, eventually. They overdesign engines because some people are hard on their cars and for Mustangs, they know that a lot of people will modify it. That's just sound engineering, always overdesigning for safety. It's true for buildings, highways, cars, anything that's properly designed!
For example, I am not an automotive engineer, but I can bet that the Mustang GT was tested with 85 octane to see what would happen. The engineers probably looked at the data and decided on changes that would ensure that if someone accidentally put 85 octane it, then it wouldn't cause major damage or come back for repairs. Ford is smart enough to know that someone in Nevada or another western state is going to try to save a few bucks or make a mistake and put 85 octane into the thing. It may not be good for the engine overall, but rest assured that Ford thought about it when they designed the car.
A tuner, however, is a sophisticated hacking. It is safe, but only for that recommend octane. It's been engineered to give the most power for that particular octane. It hasn't been engineered to provide a bulletproof safety measure in case you use the wrong octane. It hasn't been overly engineered to protect you from yourself!
Quoting the Mustang GT owner's manual:
Your vehicle is designed to use "Regular" unleaded gasone with pump (R+M)/2 octane rating of 87. We do not recommend the use of gasoine labeled as "Regular" that are sold with octaine ratings of 86 or lower in high altitude areas.
If regular gas in your area is 85 octane, then do not burn it in your Mustang.
Each vehicle is different. Sometimes, running a lower octane won't hurt your engine, it just lowers power and runs rough. You should consult your manufacturer, owners manual, or other trust source before using an octane lower than the recommended octane. For our cars it's pretty easy, 87 octane for stock or if your car has a tune use the octane that your tune requires.
Your car will be it's most efficient, get the most horsepower, and run it's best with the recommened octane, not with a higher octane and certainly not with a lower octane.
That's the great part of Mustang GT's...all that HP on 87 octane! Decent gas mileage, too. Cheap to buy, cheap to fix, cheap to run, cheap to modify, that's the best part of the Mustang (and probably why it will out sell the new Camaro, but that's another thread!).
To answer your question:
Car manufacturers have to overdesign their vehicles for everything. If it takes a higher octane, then they know that some person will make a mistake and put 87 octane in it, eventually. They overdesign engines because some people are hard on their cars and for Mustangs, they know that a lot of people will modify it. That's just sound engineering, always overdesigning for safety. It's true for buildings, highways, cars, anything that's properly designed!
For example, I am not an automotive engineer, but I can bet that the Mustang GT was tested with 85 octane to see what would happen. The engineers probably looked at the data and decided on changes that would ensure that if someone accidentally put 85 octane it, then it wouldn't cause major damage or come back for repairs. Ford is smart enough to know that someone in Nevada or another western state is going to try to save a few bucks or make a mistake and put 85 octane into the thing. It may not be good for the engine overall, but rest assured that Ford thought about it when they designed the car.
A tuner, however, is a sophisticated hacking. It is safe, but only for that recommend octane. It's been engineered to give the most power for that particular octane. It hasn't been engineered to provide a bulletproof safety measure in case you use the wrong octane. It hasn't been overly engineered to protect you from yourself!