Can someone explain the whole higher octane gas is not better thing?

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Octane # is essentially a resistance to igniting. So a higher octane is harder to ignite than a lower octane #. High compression engines use higher octane because if they didn't, the fuel would ignite on the compression stroke before the spark plug created a spark and the engine would knock.

If you run high octane in an engine that doesn't need it as knock prevention, then you would suffer lower power from the fuel being harder to ignite.
 
Some places put additives the higher octane gas to help keep the engine cleaner. Other than that, if their cars are not pinging then there's no reasone to run higher octane in those cars.
 
On a stock car, the owner's manual will tell you which octane is recommended.

When you start modifying the car, like higher compression and or a more aggressive timing curve, you then need to run a higher octane to prevent detonation.
 
illwood said:
On a stock car, the owner's manual will tell you which octane is recommended.

When you start modifying the car, like higher compression and or a more aggressive timing curve, you then need to run a higher octane to prevent detonation.
:Word:
 
Interesting. The whole cleaner thing was shot down years ago by congress. One of the gas companies were claiming that there gas was cleaner by directing your attention to a clear glass window in the handle of the pump - Amaco I think. That advertising was banned because they rules out the possibility of one gas being cleaner than another as false advertising. If you want your car to run cleaner, put some additive in it from Pep boys to clean the injectors. You would think that if the 93 is less combustable then the car won't run as well with 93 if it is supossed to have 87. Wouldn't that result is lower efficiency and worse gas mileage? Any chemical engineers want to comment?
 
Some folks do notice slightly higher milage with higher octane. :shrug: I also wonder if a bit has to do with the additives that Mike mentioned.

Nacho, if you're not pinging now (on lower grade fuel) and you didnt change timing, you very likely DID improve performance.

To answer your question another way, another time to up the octane is when one sees pinging and cant back timing down anymore. At that point, higher octane can be appropriate.

Your parents cars' likely have knock sensors, which kinda adjusts for fuel grade anyhow (to an extent).

Good luck.
 
Punisher302 said:
so if you bump the timing up, to say 14*, which octane should you run?

87. if it pings, back the timing down. Running higher octane just to have a more agressive timing curve is like putting a humidifier and a de-humidifier in the same room and letting them battle it out. Very counter-productive.
 
not trying to steal the thread, but my car is bone stock with 150k on the odometer and the timing has not been fooled with to my knowledge, but if i run anything but 93 octane, it pings and knocks like a diesel...anyone know what would cause this?
 
95five-oh said:
not trying to steal the thread, but my car is bone stock with 150k on the odometer and the timing has not been fooled with to my knowledge, but if i run anything but 93 octane, it pings and knocks like a diesel...anyone know what would cause this?
1st thing to do would be to check the timing and repost results...and go from there..
 
95five-oh said:
not trying to steal the thread, but my car is bone stock with 150k on the odometer and the timing has not been fooled with to my knowledge, but if i run anything but 93 octane, it pings and knocks like a diesel...anyone know what would cause this?

Yup, as bill said, check your base timing with the spout out. It could have been bumped. Also check your balancer for rubber degredation as this will make your timing light useless.

But a search on this forum for "pinging" will bring a multitude of solutions and the implimentations of these fixes, first and foremost being cleaning the MAF/IAT and checking the ECT's proper operation.
Scott
 
Also usually a lower octane fuel is a faster burning fuel, know as fast burn. Race gas has a lower burn rate, however some race gas is formulated to be a faster burn than others. So if that is confusing than just remember that pump gas usually has a faster burn rate than av gas or race fuels.
 
One more note, usually this is why it is very important when selecting fuels or building an engine, you must build the engine around what fuel you will be using to make the most power. This isn't neccessarily as important for street cars running on pump gas as it is for purpose built race engines.
 
mo_dingo said:
87. if it pings, back the timing down. Running higher octane just to have a more agressive timing curve is like putting a humidifier and a de-humidifier in the same room and letting them battle it out. Very counter-productive.


So are u saying that you wont see any improvement when bumping the timing and running 93 to eliminate chances of pinging?:shrug: