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Pre-ignition (or preignition) in a spark-ignition engine is often confused with engine knocking. In fact, it is a different phenomenon, when the air/fuel mixture in the cylinder ignites before the spark plug fires. It is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events. Dieseling or run-on is the same phenomenon, but refers to the engine continuing to run after the ignition is shut off with a hot spot as an ignition source for the fuel air mixture. Because both preignition and engine knock sharply increase combustion chamber temperatures, either effect can increase the likelihood of the other effect occurring. Given proper combustion chamber design, preignition can generally be eliminated by proper spark plug selection, proper fuel mixture adjustment, and periodic cleaning of the combustion chambers.
I know I think a website should get a database of all of them in each state, I think this Ethanol thing is out of control. The tree huggers are trying to save the world and at the same time are starving children because corn is being used for fuel not food.
Do you know that Ethanol while it burns cleaner in cars causes more pollution to to the manufacturing of it? This is flat out truth so all you peace-nics can shut up now.
Also I donno if all the shells have not Ethanol but the one near my house has the Premium with says no Ethanol, all other grades have 10%. Also I see a couple stations around town that have banners that say we sell 100% Gasoline-No Ethanol.
Tree huggers? You are way off the mark!!! do some reading and then you'll know who's behind the gas deals... I tell you what it's a beautiful morning here in central texas i'm going for a drive in MY BRAND NEW, SHINNY, SPARKLING, CUTE LITTLE SMART, AND I'M GOING TO TOP IF OFF AS A TREAT, THEN I'M GOING FOR BURGERS!!!! go ahead...Stay in the computer and chat. I'll check back tonite...
And I'm going real peace-nic tree-hugger and WALKING to our neighborhood farmer's market where I'm going to buy local, organic veggies I have to walk off the sausage and eggs and coffee.
And you are right, it is a beautiful day (aren't they all?) and sitting in my cave in front of the computer is no way to spend it.
For those who want to get ethanol-free fuel, consider this: 10% ethanol serves the same purpose as MTBE, used pre-1980s. MTBE is a carcinogen, and when burned in 10 million cars in Los Angeles, adds up fast. I'm not sure if MTBE was banned nationwide or just in most states, but if your choices end up being between those two, you're better off with ethanol.
And I don't think the MPG difference is 10%... maybe 2%-3%, because a gallon of pure ethanol has about 30% less energy than pure gasoline and you're only replacing 10% of your intake.
I have no formal training in automotive mechanics, so anyone with more knowledge and experience, correct me if needed.
Here in Virginia MBTE is banned and only EPA spec ethanol can be used to increase the anti-knock index. The percentage of ethanol can vary between 7.3% and 10%. The VA DEQ's official estimate of loss of efficiency is 1%-3%. Like many other places, there are additional requirements for "oxygenated" fuel blends, but that is an air quality issue not octane number.
Living in Denver in the 80's it was mandated that the Front Range community, i.e. Denver and the surrounding counties must use only "oxygenated" fuel additives to help reduce the Denver pollution problem. To that end MBTE and ethanol were both available. Living at high altitude means your mileage suffers compared to sea-level driving and then to top it off they throw in those two. Combined mileage was nearly 15% lower than my vehicle would get at lower elevations. MBTE was later phased out since it was found, oops, it'll cause you to grow various cancers.
FF to 2008 - gas in lots of FL stations now have a 10% ethanol mix. My overall mileage on my '04 Murano (from the onboard computer) was 22.8 mpg combined city/highway, with mostly city driving. It would increase to over 25mpg if I made a long highway trip. Now that the ethanol mix is being burned, my mileage has dropped to 20.2 mpg or an average of 2.6 mpg. That is certainly 10% and a smiggen more.
<rant> Ethanol is not the panacea most would have you believe. It absorbs water in storage, must be shipped by trucks (no pipelines around the country) and takes huge amounts of water to produce. . . not counting the fuel, fertilizer, etc. to grow the corn, harvest it and get it to the ethanol plant.
A totally better choice would be hydrogen. Not the reinvent-the-wheel fuel cells, plus motors, plus newly designed cars, etc. I mean plain old hydrogen gas produced by electrolysis from water. If this had been seriously pursued in the '80's instead of dinking around with ethanol, we would have hydrogen fueling stations across the country today. Hydrogen can be used in today's internal compustion engines with minor modifications and is cleaner burning than ethanol will ever be. </rant>
I have to walk off the sausage and eggs and coffee. 
Today
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