What octane gas are you guys running?
08-18-2009, 12:07 PM
#1
TECH Enthusiast
Thread Starter
What octane gas are you guys running? I have the following options
87, 90, 91, 92, 94
87 and 90 are both "regular" and cheap
91 92, are a bit more
94 is another 30 cents a gallon or so...
So what do you guys think? What should I run?
87, 90, 91, 92, 94
87 and 90 are both "regular" and cheap
91 92, are a bit more
94 is another 30 cents a gallon or so...
So what do you guys think? What should I run?
08-18-2009, 12:56 PM
#4
12 Second Club
Octane helps prevent detonation and knock caused by high compression. With Iron heads a good rule of thumb is 8.5:1 87 octane, 9.5:1 89 octane, and 10.5:1 91 octane. With Alluminum heads you can go .5 point of compression higher, 11:1 for 91 octane. My Jeep runs 8.5:1 compression with an iron head and gets only 87 octane. It's a tractor motor so that works.
Remember that this is effective compression that matters. an 8.5:1 compression turbo motor makes much more effective compression and therefore requires higher octane fuel.
The Camaro gets only 93 octane Chevron gas. I've noticed a substantial decrease in performance at the track running other brands of premium fuel. This is without any major modifications or tuning. In fact, the automakers use Chevron gasoline with Techron for EPA testing, even though they do not market gasolines in the Midwest (they haul from Louisville KY).
Remember that this is effective compression that matters. an 8.5:1 compression turbo motor makes much more effective compression and therefore requires higher octane fuel.
The Camaro gets only 93 octane Chevron gas. I've noticed a substantial decrease in performance at the track running other brands of premium fuel. This is without any major modifications or tuning. In fact, the automakers use Chevron gasoline with Techron for EPA testing, even though they do not market gasolines in the Midwest (they haul from Louisville KY).
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08-18-2009, 01:09 PM
#8
12 Second Club
Also beware of gas stations that offer a lot of octane options. Typically a gas station gets two or three gasoline mixtures. If a station gets only 87 and 91 all they have to do to pump 89 is mix 50/50. Look carefully at a pump below where the display is and you can see a analog gauge that displays how many gallons of each type of fuel has been dispensed. If there are only 2 gauges that pump mixes premium with regular to get mid-grade.
Newer pumps with only one hose are another thing to look out for. If you need only a couple of gallons of premium fuel and pull up to a single hose pump that just dispensed regular fuel, guess what. You are paying premium prices for the regular fuel in the hose.
Not all 93 octane gasolines are the same due to the R+M/2 method of calculating octane.
R stands for Research Octane Number (RON)
M stands for Motor Octane Number (MON)
So R is more of a scientific calculation and M is more real world. If your fuel supplier has a high R number and a low M number he may be selling you 93 octane gas with a real world capability of 91 octane gas.
Newer pumps with only one hose are another thing to look out for. If you need only a couple of gallons of premium fuel and pull up to a single hose pump that just dispensed regular fuel, guess what. You are paying premium prices for the regular fuel in the hose.
Not all 93 octane gasolines are the same due to the R+M/2 method of calculating octane.
R stands for 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.
M stands for 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 done at 900 rpm instead of the 600 rpm of the RON[2][3]. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a 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. Normally, fuel specifications require both a minimum RON and a minimum MON.
08-18-2009, 01:18 PM
#9
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I run 93 bc my fuel maps are only for 93 courtesy of my tuner 
Untuned cars have a lower octane fueling table that the computer can go to if you use reg gas. That being said, before my car was tuned I still ran 93. My DD and my wife's Durango gets 87.
Untuned cars have a lower octane fueling table that the computer can go to if you use reg gas. That being said, before my car was tuned I still ran 93. My DD and my wife's Durango gets 87.
08-18-2009, 01:20 PM
#10
TECH Enthusiast
08-18-2009, 06:22 PM
#20
TECH Fanatic
Yeah, that is Premium gas in Oregon too. It's 87 regular, 89 Plus, and 91 Premium.
The Gov. just signed a bill last month that exempts 91 octane and higher from the 10% ethanol mandate, so at least that is something. I wish I could buy 93 but it ain't around here.
The Gov. just signed a bill last month that exempts 91 octane and higher from the 10% ethanol mandate, so at least that is something. I wish I could buy 93 but it ain't around here.