From 91 octane to 89 octane

[RJAY]

Would it hurt my car if I switch to 89 octane gas from 91 octane gas? Gas prices are really high these days. Thanks

[GTS LAID]

you'll probably start getting engine knocking since the car requires 91.. and as summer approaches.. well i dont see the knocking getting better in the summer...

[RJAY]

What's engine knocking? Is it bad? Sorry but I'm kinda new at this.

[HilfigerCelica]

Don't be cheap. Go for the 93 octane since you have a high compression motor.

[LordZelica]

Well, actually in most part of CA (at least so CAL) the highest is only up to 92 in most gas station

[mamba]

Hmmm,
here in Australia standard Unleaded is 91 octance, Toyota say not to use it. The fuel cap has a warning saying Premium unleaded 95-96 octane, many Celica owners here use Ultimate at 98 Octane. Do they detune the engine for the US market?
Still, I think 89 must be pushing it for a GTS...

http://www.bp.com.au/products/fuels/bp_ultimate/ultimate.asp?

[RJAY]

Thanks guys

[oldster]

Originally posted by mamba
Hmmm,
here in Australia standard Unleaded is 91 octance, Toyota say not to use it. The fuel cap has a warning saying Premium unleaded 95-96 octane, many Celica owners here use Ultimate at 98 Octane. Do they detune the engine for the US market?
Still, I think 89 must be pushing it for a GTS...

http://www.bp.com.au/products/fuels/bp_ultimate/ultimate.asp?

I believe the octane is rated differently there.

[phatboypinoy510]

man its hella gay here in northern california, becuase we only have upto 91 octane... heh its ok for da accord... and i don't need gas for da rx7 cuz its broken... but i don't want to hurt my new baby!!! damnit....oh well i guess it has to live wid da 91 octane fuel

[VZV21]

You have knock sensors.

when the knock occurs with the 89 octane, the sensor send a signal to the ECU telling it to retard the spark timing.

You'll probably feel a performance decrease using 89 octane.

[RJAY]

But does it hurt the car?

[VZV21]

No it won't.

It would, if it the knock sensor was broken.

[RJAY]

Thanks

[SC3]

I wouldn't do it especially for high compression engines, where prevention of detonation is an issue. Even mild knocks puts unnecessary stress on the engine. Ignition retardation by the ECU does not occur until after a knock has already occurred and is detected. I believe it will also limit performance at higher torque engine speeds.

A friend of mine who drives an RSX (high compression engine) reports loss of power at high end when downgrading from 91 to 89.

-SC3

[pitcrew]

Use the octane that the manufacturer calls for, no less, no higher.
Using lower, especially in the summer or in hilly areas, will decrease performance, when the knock sensor retards timing, resulting in lower gas milege which will in the long run end up costing as much as the high priced spread. Using higher than needed, contrary to bench racer's urban legend, actually decreases performance as well, and is a waste of money. Momma Toy knows best!
Engine pre-ignition knock or ping (sounds like someone shaking a tin can full of pebbles when the engine is under load) is caused by the fuel air mix in the cylinder exploding rather than burning, HAMMERING the piston before it reaches the top rather than PUSHING it back down the cylinder. The sound is caused by the piston rings reversing their direction (think of old windshield wiper blades that don't flip over when the direction reverses chattering.)
If the engine is allowed to ping for an extended time or severely it can result in broken rings, worn ring grooves, or even burn a hole in the piston, or crack the piston top. :(
If anyone wants a further detailed explanation let me know...