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Old 10-06-2012, 03:45 PM   #3
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FI guys do quite well with E85, at least the S/C and turbo Buick crowd does. It burns at a lower temperature than gasoline and some have compared it to a small intercooler. They have also upgraded all fuel system components (pump/lines/injectors if needed) and have tuned for the different AFR of ethanol.

Putting ethanol in any gas engine that's not tuned or designed for it usually results in lower mileage and less power. When E85 was whole dollars cheaper than gas, it made sense because the cost offset made up for using more E85 for the same amount of miles that gas would give you. Now that it's within a few coins, it's not worth it.

And yes, all modern cars will alter timing based on air temp, fuel octane, etc. to a certain extent, but there are still parameters outside of which it can't extend. Unless you specifically tune for it, it's best to use what the manufacturer calls for. On my '00 Blazer, I actually get more miles out of 89 than 87 - enough where it's actually cheaper to use 89. My S/C Regal required 93 so that's what it got. There was definitely a drop in power if you used anything lower because the PCM pulled timing to safeguard the engine from the lower octane. The '10 Focus sees no advantage in mileage (which is why I bought the car) for anything above 87 over the course of dozens of tanks of each grade, so it gets 87.

CLIFFor Sale: In non-forced induction cars, ethanol and ethanol blends generally result in less mileage but not necessarily better performance, unless you're specifically tuned for it.

I'd wager that the new ST would do better on E85 than gas once it's tuned due to the turbo.
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