What octane do you use?

[hihoslva]

Those of you using higher than 87 for no reason other than you think "it's better" could actually be causing problems.

Since higher octane gas is MORE resistant to combustion, you may not be burning your fuel as efficiently as possible. And as rich as our cars run, using a higher octane fuel is quite counter-productive.

And, due to the combustion resistance coupled with how we already run rich, you're most likely causing a higher concentration of unburnt fuel and carbon deposits in your engine.

Just remember - 87 gas burns "EASIER" than anything "higher grade".

The myth of more power from higher octane has been spread by gas companies - so you buy the expensive stuff. True, higher-horsepower engines may NEED higher octane fuel, but you're not gaining anything by putting it in your low-compression, stock-induction 4-banger. Except possibly reducing engine life, of course.

~HH

 

[goldstar]

I recently changed my spark plugs from BKR5E-11 (OEM for P5 and sedan) to ZFR5F-11 extended reach (JDM) as recommended by TheMAN. Up until this point, I always used 87 octane as specified by the manual with absolutely no problems.

The new plugs place the electrodes closer to the center of the intake charge and therefore may have the effect of slightly advancing the timing. Additionally, since the plug reaches more deeply into the combustion chamber the tip may run hotter, possibly leading to detonation (both plugs have the same heat range). Consequently, it was suggested that an increase in octane rating might be beneficial to counter these two effects.

As a result, I now run 89 octane fuel to be on the safe side. So far (500 miles) no detonation and a small but noticeable increase in performance.