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Old 12-04-2011, 06:27 AM   #1
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Consequences to Adding Regular Gas?

While looking at the spec sheet, I couldn't help to notice that the FR-S requires premium gas. I believe it's the first Scion to require high-octane gas, but I was wondering if I could get away with 87 octane fill ups- regularly. My neighbors have Acuras and have never added a drop of premium in either of them, and they haven't added any in the previous Acuras they have owned either. If I buy an FR-S, I do plan to keep it for about 7-8 years, but performance aside, are there any major problems with adding regular gas? Since my neighbor have been doing it for years, I'm considering it myself but I would rather hear some opinions from my fellow site members first. Thanks in advance for any input!
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Old 12-04-2011, 06:39 AM   #2
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You might want to Google up longer worded answers, but octane levels basically can be translated into combustibility... Cars that "require" it means that the engine will detonate lower than suggested octane before the desired combustion point... That leads to knocking and total engine destruction...

A lot of variable can allow someone to go below octane one of which is ambient temp... If you live in a cold environment at sea level you sometimes can with the help of weather lower your regular octane during winter... However it'll take a few full tanks of premium to get back to the levels you once were... (mixing octanes lowers it or raises it to average out) Vice versa, if your ambient temps are extremely hot, you might have to raise your octane even if your vehicle does not require it...

However with the CR at 12:1 in the FT86, I'd suggest not straying from 91 octane and always use the suggested gas...

P.S. People who put 91 in their cars that do not require it might get less power / performance than advertised hurting their own pocket books... It does not "increase" performance because you're not burning all the gas since your car can't handle the increase in octane... So unless your neighbor's Acuras require it, it would make no sense for them to fill up with 91...
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Old 12-04-2011, 06:57 AM   #3
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91 is only $3$5~ or so more per fillup.
Ignition timing is different and more strict on the high compression engine.

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Old 12-04-2011, 07:08 AM   #4
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If you are NOT going to keep the car for long a time and don't care about the marginal performance decrease, then use 91.

Feel slack for the guy who buys a car that has been filled with 91 when the engine needs a higher octane. I would be very unhappy knowing this if I was to buy it 2nd hand.

Octane's in Australia.

91 with 10% ethanol ( never touched it, never will ) $1.30-40 litre aud

95 premium ( only if Im desperate ) $1.40-55 litre aud

98 vortex,vpower etc. The good stuff. $1.50-70 litre aud

Just did a google search and found this. If it's true, I didn't know it was different in different countries. ?

Have a read"..............

Originally posted by E_SolSi@Jul 17 2005, 12:48 AM
In Europe 98-octane gasoline is common and in Japan even 100-octane is readily available at the pumps, but this octane nomenclature is misleading to Americans as foreign octane ratings are derived entirely differently from our own... So, like every other measurement system it seems that everyone else uses a different scale than we do, but unlike most other instances where we have had the good sense to create different units of measure in this case we all use the same name...
Japan and Europe use a system called RON or Research Octane Number to determine the octane rating of their gasoline, while stateside we use a system called AKI or Anti-Knock Index to determine gasoline's octane rating... Interestingly, to further complicate things it would seem that our own AKI system is actually derived from the average of the RON system and another more complicated system referred to as MON or Motor Octane Number... So, to recap our methodologies for measuring gasoline's octane rating are different, but share some common elements...
So, with the commonality of RON in mind a good rule of thumb is as follows, multiply the foreign RON Octane rating by 0.95 and you will have the US AKI equivalent.

( RON Octane Rating x 0.95 = AKI Octane Rating )
98 RON Octane x 0.95 = 93.1 AKI Octane (US measure)
100 RON Octane x 0.95 = 95 AKI Octane (US measure)

So, as you can see the 93 or 94 octane fuel we are all paying an arm and a leg for is actually quite comparable to the higher octane fuels found in Europe and Japan. The people whom have to worry about low octane rating are our friends out west in places like California that are subjected to substandard 91 octane.
91 AKI Octane (US measure) = 95.5 RON Octane
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Old 12-04-2011, 07:16 AM   #5
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In the states it's 87 - 89 - 91 just so people don't confuse my first post...

I'd say for 12:1 just play it safe and use premium (highest at pump) gas and you should be fine... For your Corolla / Camry, stick with regular...
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Old 12-04-2011, 07:43 AM   #6
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The engine will knock, the ecu will adjust and you'll be significantly down on power.

That's the best case scenario. If it can't pull enough timing, you'll just kill the engine.
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Old 12-04-2011, 08:11 AM   #7
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Where I live 93 is only 20 cents more per gallon, since it has a 12 gallon tank (not including reserve) you will spend an extra $2.40. Just buy premium :P
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Old 12-04-2011, 08:28 AM   #8
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premium...
in germany is 95oktan standard and 102oktan is premium
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Old 12-04-2011, 08:33 AM   #9
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From wikipedia...

Research Octane Number (RON)
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

Motor Octane Number (MON)
There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON.[2][3] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.

Anti-Knock Index (AKI)
In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).

Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.
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Old 12-04-2011, 08:36 AM   #10
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Quote:
Originally Posted by ryude View Post
From wikipedia...

Research Octane Number (RON)
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

Motor Octane Number (MON)
There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON.[2][3] MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.

Anti-Knock Index (AKI)
In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).

Difference between RON and AKI

Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. See the table in the following section for a comparison.
sorry, my fault
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Old 12-04-2011, 08:39 AM   #11
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sorry, my fault
It wasn't specifically directed to you, but I appreciate you're mature response my friend. We're all here to find information and share what we know
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Old 12-04-2011, 09:38 AM   #12
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Making less power out of the same amount of air+gas mixture means you will be using more gas to accomplish the same. Since 12.5:1 compression engine is designed to use premium gas to make power, just use premium gas, you'll see that it will use less amount of gas to do the same job in many conditions. Even on my (newer) Corolla, premium gas gives better power output compared to cheap regular. Even the engine sound under load is different.
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Old 12-04-2011, 09:45 AM   #13
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Well, if you have to debate or even consider 87, then you shouldn't buy this car.

High compression or FI cars require High Octane. It's not a debate. Honestly, you should look for a place that has 93 than 91.
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Old 12-04-2011, 11:32 AM   #14
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The engine will knock, the ecu will adjust and you'll be significantly down on power.

That's the best case scenario. If it can't pull enough timing, you'll just kill the engine.
It'll pull enough timing. Most NA cars these days are so good on knock retard that you'd be hard pressed to grenade a motor. Liability issues and all. HOWEVER, the money that you saved by putting regular in the car instead of premium, you lose in fuel economy because the car is going to burn that much less efficiently and you'll be using more throttle to get the same result. It ends up being a wash.
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