Man, I can't believe this blog is still around. I haven't posted in 6 years!
So the Saab is long gone. Since then I've driven a flexfuel Buick Regal, using E85 when it was economical to do so, or when I felt that a tank or two of E85 would clean out the fuel system.
Just recently, I got a 2004 Acura TL with 153k miles on it. The TL requires premium fuel, and as you may have noticed, premium fuel is very expensive these days.
When I was a young man, premium was always 10 cents more than mid grade, which was always 10 cents more than regular.
No longer. It seems that stations are using a more cost based market price for their fuels. Today premium was 40 cents more than regular. I have noticed that the premium for premium varies.
I read that US refineries are using a lot of oil recovered from fracking, which evidently doesn't have an much higher octane hydrocarbons as non-fracked oil does. Thus, it costs more to make higher octane fuels, and they're priced accordingly.
Well, what's the best octane booster around? E85, of course!
Now, it's not easy to determine what the octane of E85 really is. Meijer's sign says that it's 105 octane. I have read that E85 is between 96 and 97 octane, but I also don't think that is correct. I also have read that straight ethanol is 120 octane.
Looking through my notes, I see that when calculating octane, I assumed 100 octane for winter blend E85 (E70, really). So my calculations will reflect that, until we switch to summer blend. I think I assumed that summer blend is 105 octane and derated based on ethanol content as a percentage.
So... I put 2 gallons of E85 in with 11 gallons of 87 octane gasoline. I'm running roughly E17 and have roughly 89 octane.
I want to ease into the higher ethanol contents so as not to clean the fuel system too aggressively. I intend to limit the ethanol content from going TOO high, there is no advantage to going much over 91 octane on this engine, and with so many miles there is the risk of killing a fuel pump or some fuel system component. I'm going to be very interested to see how well things last and if I kill something quickly or not. We know from this blog that long term use of higher grades of ethanol doesn't hurt a modern vehicle, but that was on a relatively new vehicle, this is one that may have end of life components even without higher grades of ethanol. We will see what happens.
I intend the next tank to be 3 gallons of E85, which will take me to roughly E23, and maybe 90 octane. I won't go much over that.