10:1 compression ratio; 87 or 89 octane?

[Elite Engineer]

I own a 2007 toyota corolla (stick shift ). The engine is a 1.8L with a 10:1 compression ratio (stock).

 

Should I be using 87 octane or 89 octane due to the 10:1 ratio?

 

~ee

[fiveworlds]

Petrol or diesel?

[Enthalpy]

Does such a low octane exist? Or do you mean 98?

[Phi for All]

It's not going to make much difference, imo. You've got knock sensors, and your engine is made for lower octanes. You should try both and see if there's a performance issue. I'm predicting you'll get worse mileage with the higher octane fuels.

[Greg H.]

Does such a low octane exist? Or do you mean 98?

 

In the US (where I live) there are only a certain number of octane levels commercially available - 87, 89 (which tends to be blended with ethanol) and either 91 or 93 (I have never seen both levels offered at the same station, and the choice seems to be regional, which 93 being more readily availble in the Southeast, 91 in the midwest). I have seen a very few stations that offer octanes in the 101-104 range, and these tend to cost considerably more than the other options.

[fiveworlds]

I'm predicting you'll get worse mileage with the higher octane fuels.

 

Usually yeah. The amount of fuel per liter is less since its a mix in higher octane fuel. Octane rating only denotes the fuel blend's ability to resist autoignition. The only time this wouldn't be true is in engines where the complete burning of the higher octane fuel. Burns at a higher temperature and therefore can actually give better mileage since the engine runs more efficiently. Also if the lower octane fuel ignites early before the piston completes rotation you can wind up burning a larger amount of lower octane fuel per stroke.

Edited August 5, 2014 by fiveworlds

[Elite Engineer]

Petrol or diesel?

Is this a serious question? diesel with a 10:1 comp. ratio?

[Enthalpy]

The amount of fuel per liter is less since its a mix in higher octane fuel.

 

The higher octane results from a mix with compounds (iso-octane and many more) just as good as others.

[fiveworlds]

The higher octane results from a mix with compounds (iso-octane and many more) just as good as others.

 

http://en.wikipedia.org/wiki/Acetone

http://en.wikipedia.org/wiki/Methanol

http://en.wikipedia.org/wiki/Benzole

 

http://www.turbofast.com.au/racefuel13.html

Water in Nitromethane. Up to a maximum of 2.5 percent as this is the maximum amount that will mix without separation taking place. It reduces both preignition and detonation due to the internal cooling effect alone.

 

water?

 

Is this a serious question? diesel with a 10:1 comp. ratio?

 

 

In a piston engine, it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.^[1]

^{http://en.wikipedia.org/wiki/Compression_ratio}

Edited August 6, 2014 by fiveworlds

[Enthalpy]

Diesel engines need more than 10:1 compression ratio to work. People who pointed that out need no explanation about the compression ratio.

 

No nitromethane in a Toyota Corolla, especially if the user cares about mileage. The fuel from the station doesn't contain any - and benzole is just a good fuel.

 

If the fuel of too low octane ignites early you destroy the engine, then the mileage is unimportant. And the proper octane won't let unburnt fuel at the exhaust - any effect of unburnt fuel observable on the mileage would bar the car from the roads. So for a sound car, the proper octane burns all the fuel, a lower octane won't improve.

 

In the US (where I live) there are only a certain number of octane levels commercially available - 87, 89 (which tends to be blended with ethanol) and either 91 or 93 [...]

 

Thanks! Wider choice there than here (95 and 98, no low octane).

Edited August 7, 2014 by Enthalpy

[MigL]

Where is 'here' Enthalpy ?

I've personally never seen higher than 94 for pump gasoline.

Octane booster or AV gas are usually 98 to 104.