On 2001-07-23 13:15, VPRKLLR said:
GM states that only three of their engines require 93 octane fuel.
The three engines are:
- Chevrolet LS1
- Chevrolet LS6
- Cadillac Northstar
Well---this is not quite accurate. What GM says is: premium fuel is *recommended*. It's a minimum of 87-octane gas that's required. C5s will run on 87, though not very well. They will experience a lot of spark retard via knock sensor input until the PCM learning ability alters the spark curve to be less aggressive and they will have a noticeable loss of performance.
I've seen two figures from GM as to the recommended octane for the LS1/6 engines: 93 and 91. Why the confusion? I'm not sure but I suspect the actual recommended number is 91 because that's what it's been in the past.
In any event, in a practical sense, even 93 octane is not enough if we are to believe some internal oil industry studies I've seen. To keep the engines out of detonation in most atmospheric conditions and under most engine duty-cycles, some performance cars require as much as 94.5 octane.
Keep in mind it is just not the 1 octane less, it's they are sticking some other crap in the gas now to replace the other crap that they tried to shove down our gastanks as re-formulated. Be sure it will be poping up down the raod that the new crap is just as bad for injectors, etc. and adding ethanol or another additive is leading to a slightly lower octane level"
John Rovner's comments are always, uh...interesting. In this case he's wrong.
The principle oxygenate component in gasoline sold in California (and most of the west coast for that matter) is still MTBE. Ethanol is not legal as a gasoline component in California, yet, but it will be soon as the phase-out of MTBE is coming.
Another fact: oxygenates like MTBE and ethanol do not decrease octane they increase it. In fact, MTBE was originally developed as a possible octane-booster replacement for tetraethyl lead. It wasn't until later (the late-70s/early-80s) when it was discovered it could reduce exhaust emissions. Ethanol increases octane and acts as an oxygenate, too.
The reason 76 (and some other oil companies, too) reduced the octane of its premium and mid-grade gasolines was mainly for two reasons 1) the oil companies on the west coast finally gave in to the pipeline companies and agreed to stop shipping both 91 and 92 octane premium unleadeds. The pipeline companies wanted just one grade of premium gas to ship. 2) the oil companies can increase gasoline output if octane is reduced slightly.
Interestingly, 91-octane premium is not, yet, nationwide. All along the eastern seaboard, 92- and even 93-octane has been common.
I have located some Sunoco Oxygenated Unleaded race gas (104 Octane) for about $ 4.40 gal. + tax. I will try to pick a drum up in my truck and give it a try this weekend.
In California there are a small number of 76 stations and even a few Cirle K's that sell 76 Competition 100 unleaded racing gas through pumps. I buy 100 unleaded from a 76 station right near my home. My understanding is you can go to to
http://www.76.com to find the locations of these stations.
To keep a Z06 out of detonation in all weather conditions and under any load my guess is you need 94.5 octane which is a mix of about 2:3 76 Comp. 100 to 91-oct. pump gas
