91 Octane Rating

Out here in California, the Oil Companies in their infinite greed have decided to add more ethanol to the gas mixture. The result is that the highest octane we can get in our gas is 91. Down from 92. Any opinions on this? What will be the short/long term effects to my engine? Should I be using octane booster?

I noticed one Union 76 station in L.A. dowgraded from 92 to 91 but none other than this particular one. Since I didn't see another 76 doing the same, I assumed the particular station had switched suppliers.

Yeah. I had noticed it at a gas station I frequented and thought the same thing as you. However, I saw a news story the other night, that with the phase out of MTB the oil companies are adding more ethanol and soon we won't be able to find 92.

Although I think you have a right to be mad, I take some exception to the allegation that ethanol is appearing in your gasoline because of oil company greed - I work for one of those energy companies. The truth is that your California Air Resource Board has mandated oxygenates in gasoline for several years. In the last year, California has decided that MTBE is bad because it can leach in groundwater from leaking tanks at filling stations. Rather than fixing the tanks, they want something more innocuous; hence you are now getting ethanol. Expect this to happen on a nationwide scale if MTBE ban in CA dominos to other states. You should read your owners manual about the suitability of ethanol in gasoline - I think Porsche really doesn't like it much. BTW: you can probably thank your local corn producers and the associated ethanol lobby for the push to put it in gasoline - with the exception of ARCO, the oil companies have never really favored alcohols or oxygenates as a fuel component. BTW2: your tax dollars are subsidizing the use of ethanol as a fuel - just think of it as another way to pay our US government for driving your car.

Yes, the news story I heard was what JBH is describing. Another mandate from the Golden State disallowing MTBE and replacing it with ethanol which (for now) can only come from the midwest.

A certain gigantic midwestern commodities company is one of the largest political contributors in the nation.That's why our Porsches will soon be running on Iowa corn power here in California, to the detriment of our fuel systems. Because MTEB made up 10% of the volume of our pump gas, the much smaller volume needed of mixed -in ethanol would have lead to a 10% shortfall in gas supply in gas guzzling truck/SUV crazed California , so the main pipeline company reuced octane from 92 to 91 to ensure ample gas supply, as most drivers couldn't care less about the octane needs of expensive foreign cars. At least that's the official explanation .

While I'm not a big fan of ethanol in gas I'm not sure you can blame it for lower octane. We've had mandated 10% ethanol in MN for a couple of years and can still buy 92 and 93 octane gas. I have no clue about the chemistry of the fuel though.

Yep, this 92 to 91 deal has happened in SD, CA in just the last week. It really does suck as I was already coming down from 93 in Fla :-(

As JimB mentioned, we've had state-mandated ethanol as an oxygenate here in Minnesota, for more than a few years (maybe as many as 10). It's harder to find high-octane fuel, but there are still 92 and 93 octane premiums to be found and a very few stations carry higher than that. Ethanol has lower energy per volume than gasoline, so you lose performance and mileage with an ethanol blend. I'm not sure what affect it has on octane, if any. It's probably less likely to detonate than gasoline, and if so, might actually raise the octane value which is really an anti-knock index these days. Ethanol is not particularly good for a number of materials that were often used in fuel systems, but I don't know to what extent modern cars suffer detrimental affects, if any, from it.

Sorry - I should have answered the issue of octane earlier. Ethanol - ~106 MTBE - ~116 Without know how the blending was done, it's not possible to say the substitution of ethanol for MTBE was the reason. Might have been, but then again perhaps the octane pool is short and the refineries couldn't make the higher rating and still stay within the limits for oxygenate blends (as suggested above). One thing about oxygenates is they have the effect of leaning out the mixture when injected and combusted in your engine (that's how they reduce carbon monoxide emissions). If you are running a turbo, you need to be very careful about any change in oxygenate type or concentration. I am not sure how, if at all, the actual oxygenate content of your fuel has changed in California. Anyone tried octane boosters?

I did a little more reading on this subject. Turns out, you can thank George W. Bush for the ethanol in the CA gasoline, and most likely as a result, the 91 octane. Turns out that California wanted to mandate oxygenated gasoline to decrease pollution -- which it is very effective at doing. California and the petroleum companies wanted to use an oxygenate that is not only cheaper, but works better than ethanol. California's arguments for relief from fuel-additive requirements are persuasive. In rejecting them, the Bush administration offered no convincing environmental justification. As MKW pointed out, several very large midwest ethanol producers in the midwest did some lobbying of the regulators. I live in Minnesota: we subsidize the ethanol produces in this state, we produce more ethanol than any other state, and yup, we sell it to California as well as other places. I can't say that I like it. There's an editorial in today's Minneapolis Star Tribune newspaper about this very topic: it'll be around until late tonight when they post Monday's editorials at this URL: http://www.startribune.com/viewers/q...n_a&slug=ED29A Star Tribune ethanol editorial