Originally Posted By: Nyogtha
Originally Posted By: Vern_in_IL
Ethanol free 93??? I DON'T THINK SO!!
If it was ethanol free, it should read 91 (add the corn to raise it to 93)
I was blending ethanol free 93 (R+M)/2 gasoline in 1991. It was also MTBE and lead free. Otherwise known now as conventional gasoline.
Someone has quite a paradigm.
I'm pretty sure that these days there's more demand for premium unleaded with even econoboxes specifying 91 octane. Of course ethanol is probably the most effective octane booster available outside of lead.
I remember hearing about the "math exercise" in this article (or at least the original version which seems to have disappeared from the internet). It probably oversimplifies things, but it simplifies things enough to get why you can't just make as much 93 octane nonethanol unleaded as you want.
Quote:
http://www.smokinvette.com/corvetteforum....html#post20329
You see, when crude oil is refined into gasoline, the refinery doesn't have all that much control over what comes out. Crude oil is full of all kinds of stuff, and a refinery simply separates it, sorting all the iso-this and hepta-that in order of density. The really heavy stuff, like tar, is near the bottom, while the really light stuff, like butane, is near the top.
Somewhere in the upper ranges of the stack are the components of gasoline. There are between 10 and 15 different blend stocks, each with a different octane rating, which are mixed together to make gasoline.
The crude oil being used and little else determine the amount of each blend stock available for mixing. Generally, if you just dump all the blend stocks into a bucket, you end up with something around 88 or 89 octane. If you're selective and only mix the good stuff, you can make 92, 93 or even 95 octane. But once you take out the good stuff, you're left with [censored]--something like 85 octane. Then you have to leave enough good stuff in the bucket to bring this pee-water up to at least 87 octane. This limits the amount of 95-octane gas you can make. If you make 93-octane premium instead, you use up less of the high-octane stocks, allowing you to make a higher proportion of premium fuel.
In the Midwest, where an extensive customer base of good old boys in pickup trucks consume vast quantities of 87 octane, demand for premium fuel is low enough to make genuine high-octane premium.