# Does hjgher octane gas cause more carbon build up?



## dschrier (May 6, 2002)

Alright, I know this question has been asked many many times, but I only want to know, will using 89 or 91/93 octane in my sentra 1.8 cause more carbon build up than using just 87. I know that there will most likely be no performance gain and no better gas mileage increase. It used to be, some say anyways, that the higher octane gas had better cleaners in them, but now all gas is supposed to be the same aside from cleaners. I've heard that using higher octane gas will cause more carbon build up, but others say that using a slightly higher octane rating, say 89 instead of 87 may fight off the knock/ping caused by a bad batch of gas and offer a little more protection. I know I'm opening a can of worms here, but will higher octane harm my engine? That I guess is the ultimate question.


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## Katana200sx (May 13, 2002)

actually higher octane gas will help clean your engine out some bc it burns hotter than a lower octane gas.


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## dschrier (May 6, 2002)

I've read before that higher octane gasoline used in a car which doesn't require it will cause more carbon build up due to the slower burning of the fuel. Of course this could have been stated long ago when fuel and engines were much different than they are today.


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## bahearn (Jul 15, 2002)

Higher octane gasoline does *not* burn hotter.

Modern street high octane gas will take a long time to carbon up your combustion chamber. Race gas is s different story since they typically use aromatics to attain their octane gain. The aromatic components are what coke up in your engine.


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## dschrier (May 6, 2002)

So would running 89 octane in my car cause any harmful side affects to the engine in the lifespan that I might own the car for?


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## bahearn (Jul 15, 2002)

The only harmful side effect would be your artificially low bank account. The only reasons to go with higher than 87-octane are bumped timing or already-coked cylinders.


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## johnebp (May 8, 2003)

from what i've read...

Regular octane (89) is recommended for most cars. Suped up and turbo cars need the higher octanes to prevent knocking.

EVERY level of octane contains the same amount of carbon deposit preventing additives, this is by national law.

Fuel system cleaners supposedly do work, once or twice a year put a bottle in your system to help against carbon deposits.

So basically, if you're not knocking, then you're fine.


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## psuLemon (Apr 23, 2003)

actually, i believe that it should burn cleaner with a higher octane, i know cars run better with higher octane.. i dont use anything less than 89...


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## bump (Jul 8, 2003)

on some cars stock you must use high octane gas. they have high compression ratios, like my moms acura that she killed. it still runs, but it smokes like a fucking train, and its only a 96. its because shes too chep and used 87 when she needed premium. it even says that on the dash


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## johnebp (May 8, 2003)

if you modify your engine, ask someone, if not, check your car's manual, it'll tell you.


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## ForsakenRX7 (Mar 14, 2003)

High compression cars, turbo cars, and supercharged cars need high octane to prevent pinging and detonation. The standard naturally aspirated vehicle (like a stock 200sx for example) does NOT. Yes, believe it or not using high octane in a normal car can cause carbon build up over time because when using Supreme or hi octane in a non turbo, the higher octane makes it more difficult to burn all of the fuel allowing for excessive carbon. Trust me, I drive a rotary car. Carbon build up knowledge is key to a rotaries survival.


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## bahearn (Jul 15, 2002)

Rotaries coke because of oil leaking past the end seals.

Modern high-octane gas won't coke up like the old formulas.

*Psulemon*, you'll change your BELIEF after reading _"The Internal Combustion Engine in Theory and Practice"_ by Charles Taylor. There are two volumes, Vol. 2 will suffice for this conversation.


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