Is 89 octane ok to run?

**estrellajon** · 03-07-2005, 07:21 AM

I have a C280 and run the required minimum octane according to the manual. Has anyone ran 89 octane? Is there a performance difference or problems?

**Ashkan's C280** · 03-07-2005, 07:26 AM

i ran 89 for a while, nothing happened... but when i put in 91 it felt like it had more jump or something maybe it is in my head but it feels like I have more pull with 91

**sleek_benzo** · 03-07-2005, 08:15 AM

damn shitty california 91 octane POS!!!

**estrellajon** · 03-07-2005, 08:20 AM

so running 89 wont hurt the motor? what about 87?

**alphanumeric** · 03-07-2005, 08:45 AM

the only difference from my experiance is less power... it especially hurts performance in a turbo or supercharged engine..but for a dialy driver.. I do not see the harm in running 87.. I have ran 87 octane in my 2000 Jetta 1.8t and it now has over 100,000 miles!!! and no problems at all.. and all thats ever been done to it was oil changes LOL...

BUT I now run 91 octane in my c230k and the wrx.. it just makes me feel better.. after reading this thread tho. I might fill up on 87 from here on out..

**martattack** · 03-07-2005, 09:15 AM

My manual, and even the sticker on the gas filler door says to use Premium Unleaded Only. So that's what I do.

**alboogiee** · 03-07-2005, 09:56 AM

Originally posted by sleek_benzo
damn shitty california 91 octane POS!!!

i sooo agree, im originally from chicago and the max is 93.. there isnt much of a diff between 89/91 but if you are really an enthusiast, go with 91, your car will appreciate it especially if you are heavy on the pedalâ€¦ but if you are running 89, and want to upgrade to 91, disconnect the battery for approx 5 min, this will reset the ecu and it will remap itself to run with 91, when you are consistently running 89, or shitty lets say arco gas your car compensates for the lack of octane. I got this info from a write up in modified mag or import tunerâ€¦ about 5/6 months agoâ€¦ they did it to a Subaru wrx running 89 then switched it to 91, gained roughly 3/4 horses

**Renn 208** · 03-07-2005, 11:10 AM

to get to the question of "how low can i go?"

Your engine will run fine on lower grade gas to a point. As we're talking about modern cars, the ECU will just pull timing if it encounters knock. Performance decreases...but it does no real harm.

Another thing to take into account is if your mpg decreases with lower octane gas. If that's the case, your $/gal savings might be wiped out by the use of more gas.

On the opposite side of the spectrum, if you have a car that is already at optimal performance with 91 octane, putting in higher octane gas will not gain any performance in and of itself.

Only when mods come into play does even higher than pump octane become useful. If you're running additional boost, higher CR than stock, that sort of thing, then resistance to knock becomes more of an issue.

If you start to get spontaneous detonation (knock)...that's definitely not a good situation.

**Dr.Drew** · 03-07-2005, 11:40 AM

if you dont accelerate at more then 3000 rpm then regular gas is fine, i personaly use the highest octane i can find either 92 or 94 i like to drive it higher then 3000rmp and you can feel the difference, the only problem with 94 is you may eventually burn out your piston, but i think these cars can handel it.

its a benz were talking about dont cheap out on gas.
its like a $1.50 more per fill

**sleek_benzo** · 03-07-2005, 12:06 PM

Originally posted by Dr.Drew

its like a $1.50 more per fill

would like to know where you fill up..

its about 2.30+ per gallon

**Dr.Drew** · 03-07-2005, 12:20 PM

Canada lol

**manny** · 03-07-2005, 12:32 PM

Originally posted by Dr.Drew
[B]the only problem with 94 is you may eventually burn out your piston, but i think these cars can handel it.
/B]

You must have failed the Mechanic's class in High School.

**sleek_benzo** · 03-07-2005, 12:42 PM

errrhhh.. damn canadian..

beautiful country.. friendly people (very friendly

)

**manny** · 03-07-2005, 12:50 PM

We're still # 1 in the world as far as per capita beer consumption goes.

**sleek_benzo** · 03-07-2005, 01:19 PM

is that why the female are you friendly?

i love me a canadian chick.

**BLKc230** · 03-07-2005, 01:22 PM

is some gas really better then others (Arco, Cheveron, Shell, 76. ext)

**Dr.Drew** · 03-07-2005, 01:26 PM

You must have failed the Mechanic's class in High School.

elaborate please, running higher octane that recomened will burn a hole through your piston

**manny** · 03-07-2005, 02:16 PM

Originally posted by Dr.Drew
elaborate please, running higher octane that recomened will burn a hole through your piston

That's the funniest thing I've ever heard.
Higher octane means higher resistance of the fuel to self-ignite.
I.e. it is HARDER to ignite high octane gas, therefore it allows you to run more advanced ignition timing, which will result in a peppier, more powerful engine.
All High Performance chips increase ignition timing ( aside from adding more fuel ), that's how they can squeeze a few more horsepower from the engine.
Burned pistons are normally caused by TOO LEAN a fuel mixure.
Running a low octane fuel on a high compression engine ( without computer-controlled timing ) can result in " pinging" or " knocking " which can also lead to a " holed " piston in short order.
Anything else ?

**martattack** · 03-07-2005, 02:16 PM

Originally posted by Dr.Drew
elaborate please, running higher octane that recomened will burn a hole through your piston

It will probably blow the headgasket before it burns a hole in the piston.. but anything can happen with detonation (pinging), which is what happens when your octane is too low.

**manny** · 03-07-2005, 02:32 PM

Originally posted by sleek_benzo
is that why the female are you friendly?

We have friendly Guys too.

**jnolte** · 03-07-2005, 02:45 PM

Originally posted by sleek_benzo
is that why the female are you friendly?

i love me a canadian chick.

i gots me a canadian chick!

**alboogiee** · 03-07-2005, 03:29 PM

Originally posted by BLKc230
is some gas really better then others (Arco, Cheveron, Shell, 76. ext)

in my opinion it is, your from bay area so you know about travis afb...i used to fill up there, but i switched to shell/chevron b/c i noticed that i would get roughly 300/350 miles per tank rather then 250/275 a tank...in my opinion there is better/shitty gas i dont think it is like people say though... "watered down"

**manny** · 03-07-2005, 06:18 PM

Originally posted by jnolte
i gots me a canadian chick!

Congratulations.
They're pretty low maintenance.

**estrellajon** · 03-07-2005, 07:15 PM

Well here's the results. I filled up with 89 octane and drove 50 miles. Mixed driving from stop and go and highway. There is definitely a very slight decrease in power on the stop and go, however, I did not notice it on the highway. The car ran fine and smooth and did not knock or ping like I thought it would.

**Renn 208** · 03-07-2005, 08:31 PM

Originally posted by estrellajon
Well here's the results. I filled up with 89 octane and drove 50 miles. Mixed driving from stop and go and highway. There is definitely a very slight decrease in power on the stop and go, however, I did not notice it on the highway. The car ran fine and smooth and did not knock or ping like I thought it would.

like i mentioned previously...smart new cars will deal with lower octane gas just fine. More often, it's older cars without fancy electronics that can't handle lower octane gas.

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