87, 89 or 91 octane for 87 Carrera?
03-11-2003, 09:16 PM
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87, 89 or 91 octane for 87 Carrera?
I've owned an 87 Carrera for only 2 weeks so please excuse my ignorance. I tried to search on this board but seemed to get mixed answers to what's the right octane to use for my car. So what should I use for daily street driving: 87, 89 or 91 octane? Please advise.
Thanks.
Dzung.
Thanks.
Dzung.
03-11-2003, 09:27 PM
#2
Hello PGUY,you will get mixed answers.Some will say run what the owners manual states while others will say premium while others will say to add items to enhance the octane even higher,having said that here is my 2 cents on the subject-these air cooled cars work very hard in the heat and we tend to push them pretty hard,add to that running AC and you are demanding a lot of these engines and they do not like to knock/ping,but our engines tend to be noisy because of air cooled or performance exhaust etc. and we may not here the detonation,thats a bad thing,so I only run premium in my 1983-911SC,it gives me peace of mind that I am doing what I can to help control pinging,along with keeping the car in a good state of tune.Sorry for the long winded answer,hope this helped.
03-12-2003, 01:17 AM
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DandyD is correct if the sticker reads:
OKTAN MIN
RON + MON
------------ = 91
2
91 does NOT equal 87 using this method, often referred to as "pump octane." This is the method used to compute octane ratings in the United States.
A primer:
RON = Research Octane Number. This is generally used in Europe and yields a higher rating. 87 in the U.S. is the equivalent of 91 or 92 RON, which is what Bill is probably referring to.
MON = Motor Octane Number. This yields a lower number than the U.S. Octane. 82 MON is about 87 in the U.S.
In the U.S., pump octane is achieved by averaging RON & MON, hence the formula RON+MON/2.
Therefore, if the manual or label reads: 91 RON, you can use 87 octane here in the States. If it reads 91 RON+MON/2, use at least 91!
One other note:
Many states in the U.S. require use of oxygenated or reformulated gasoline. This fuel burns cleaner, but it can slightly lower fuel economy and engine performance. If your engine is really dirty with carbon deposits, it will also cause pinging or premature burn. In these situations, you may want to consider stepping up to the next grade of gasoline.
I've personally found 87 octane reformulated fuel doesn't always work well in a performance car, even if the manual recommends the use of 87.
-Sean
OKTAN MIN
RON + MON
------------ = 91
2
91 does NOT equal 87 using this method, often referred to as "pump octane." This is the method used to compute octane ratings in the United States.
A primer:
RON = Research Octane Number. This is generally used in Europe and yields a higher rating. 87 in the U.S. is the equivalent of 91 or 92 RON, which is what Bill is probably referring to.
MON = Motor Octane Number. This yields a lower number than the U.S. Octane. 82 MON is about 87 in the U.S.
In the U.S., pump octane is achieved by averaging RON & MON, hence the formula RON+MON/2.
Therefore, if the manual or label reads: 91 RON, you can use 87 octane here in the States. If it reads 91 RON+MON/2, use at least 91!
One other note:
Many states in the U.S. require use of oxygenated or reformulated gasoline. This fuel burns cleaner, but it can slightly lower fuel economy and engine performance. If your engine is really dirty with carbon deposits, it will also cause pinging or premature burn. In these situations, you may want to consider stepping up to the next grade of gasoline.
I've personally found 87 octane reformulated fuel doesn't always work well in a performance car, even if the manual recommends the use of 87.
-Sean
03-12-2003, 12:53 PM
#6
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Pguy,
Sean's correct - RON is usually 4-5 points higher than R+M/2, so that's what I was referring to. Related to that, I find an annual tank full of Techron helps to keep the engine innards clean, especially valve deposits from the local gasoline additives. (this gets discussed periodically, there's a bunch of opinions in the archives)
Sean's correct - RON is usually 4-5 points higher than R+M/2, so that's what I was referring to. Related to that, I find an annual tank full of Techron helps to keep the engine innards clean, especially valve deposits from the local gasoline additives. (this gets discussed periodically, there's a bunch of opinions in the archives)
03-12-2003, 01:47 PM
#7
RL Technical Advisor
Pguy:
My best advice to you is to use 91 octane (pump; R+M/2) at the very least. These engines are not equipped with knock sensors and you will never hear anything going on back there,......
Given the number of these things that are found with broken rings on disassembly caused by detonation, its penny-wise and pound-foolish to use anything else but premium fuel.
My best advice to you is to use 91 octane (pump; R+M/2) at the very least. These engines are not equipped with knock sensors and you will never hear anything going on back there,......
Given the number of these things that are found with broken rings on disassembly caused by detonation, its penny-wise and pound-foolish to use anything else but premium fuel.
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03-13-2003, 09:30 AM
#9
I read an article that said that "octane boosters" are a waste of money. Basically it said that the small amount of a bottle does nothing compared with 15-20 gallons of gas. It went on to say that you would have to add a bunch of bottles to make any difference and the cost was ridiculous.
Discuss amongst yourselves. <img border="0" title="" alt="[Wink]" src="wink.gif" />
Discuss amongst yourselves. <img border="0" title="" alt="[Wink]" src="wink.gif" />
03-16-2003, 11:28 AM
#11
How about storage?
My dad told me that its a good idea to fill the tank with AV Gas right before storing for the winter. Is there any truth to this? Can running high octane like this hurt a farily stock engine?
My dad told me that its a good idea to fill the tank with AV Gas right before storing for the winter. Is there any truth to this? Can running high octane like this hurt a farily stock engine?
