Different Gas, Car feels different?? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

99-Boxster-MK · 06-20-2005, 03:29 PM

Hey all...

I have been filling up with Sunoco Ultra 94 gas (the one with 10% ethanol), as this is the highest octane gas around me, but I recently filled up with Shell V-Power gas (91 octane) and the car feels faster and smoother?????

Can it be that the boxster does not like ethanol additives in its gas?

Mike

Brucelee · 06-20-2005, 05:28 PM

I can't comment on the ethanol but I can tell you that there IS a difference in gasolines. My Porsches do better on that Shell and with Chevron.

Go figure.

bigislandboxster · 06-20-2005, 05:45 PM

Can't speak for Sunoco (no stations out here), but Chevron 92 octane w/ Techron seems to work the best for me...at $2.94 a gallon it better!

YellowJacket · 06-21-2005, 07:19 AM

Yeah, any car I've owned, I've started to notice subtle differences depending on what type of gas I use, how close I am to an oil change, the air temperature outside, whether the a/c is running, etc.

And yup -- Chevron or Amoco 93 octane is the only way to go! Although it's a little less than $2.94/gal here -- I paid $2.27 at my last fill.

MLegere · 06-21-2005, 03:37 PM

Yeah I like the Chevron 93 oct paid 2.23.

kskimtahoe · 06-21-2005, 05:20 PM

I heard that in CA there is such a strict control over what is allowed that all brands are more or less the same. Also, one of my associate who seriously looked into owning a gas station told me that as long as you buy certain amount of gas from the "parent" company (I think it was less than 50%), you can fill the rest with whatever gas you can buy. Maybe he was pulling my leg.

What type of difference do you notice between different brand of gas?

bigislandboxster · 06-21-2005, 05:47 PM

I can only dream of prices that low

.....Thats the paradise tax for ya!

jiggysubman · 06-22-2005, 08:34 AM

being in the military, the gas station on base doesn't have taxes....try $2.05

FUHRIUS · 06-22-2005, 11:06 AM

I can only find 91 octane at chevron...

though the books on the car suggest using 93 octane.

anyone ever used an octane additive in the boxster?

Brucelee · 06-22-2005, 01:04 PM

91 seems fine in all my Porsches!

Quote:

Originally Posted by FUHRIUS

I can only find 91 octane at chevron...

though the books on the car suggest using 93 octane.

anyone ever used an octane additive in the boxster?

xavier405 · 06-22-2005, 05:26 PM

Somebody told me that there was a 93 Octane available at a Chevron near John Wayne Airport (Orange County, CA). I have to go look for it.

RENNX · 06-22-2005, 08:27 PM

I saw a HUGE difference when I filled with Chevron last week, thanks to the forum.

deliriousga · 06-24-2005, 01:11 PM

Quote:

Originally Posted by 99-Boxster-MK

Hey all...I have been filling up with Sunoco Ultra 94 gas (the one with 10% ethanol), as this is the highest octane gas around me, but I recently filled up with Shell V-Power gas (91 octane) and the car feels faster and smoother????? Can it be that the boxster does not like ethanol additives in its gas?

It's probably a combo. There is a warning in the manual to stop using ethanol fuels if performance is degraded.

For the octane, the higher the octane, the lower the volatility of the gas. When you get knock from a low octain gas it's because it ignites too early due to the compression, before the spark plug fires and before the piston is finished with its' up stroke (or out stroke in the Boxster's case). That causes the upward (outward) moving piston to have force shoved against it so it knocks and looses power in its' stroke.

On the other hand, if the octane is too high, it doesn't ignite on time. The spark plug fires and it takes a millisecond longer than it should to ignite so the piston is already on its' way back down (in). When the gas ignites it pushes the piston downward (inward), but not at the optimal time. Since the piston was already moving downward (inward), it's further away from the combustion than it is supposed to be so it does not create as much power in the stroke.

Multiply these by 3K-6K times per minute and now you know...the rest of the story.

deliriousga · 06-24-2005, 01:15 PM

Quote:

Originally Posted by FUHRIUS

I can only find 91 octane at chevron...though the books on the car suggest using 93 octane. anyone ever used an octane additive in the boxster?

Don't bother with the "octane boosters". They don't boost it very much. Take a bottle that says Octane Booster 5 on it. The 5 is really only a .5 boost in octain for a lot of $$$ relatively.

Chevron gas runs better because of the Techron in it. It really does keep the system clean and keeps carbon from building up. I don't use it (get my gas at Krober), but we have 93 octane everywhere here and I drive my Porsches in the high RPM range which keeps the carbon from building up.