This Prius will be short tripped unfortunately. 7 miles in each direction for commute. On the way to it's crummy life, there is a gas station which sells 87 octane and 88 octane. Unlike what I have heard about other areas, 88 octane is notably cheaper than 87 octane here in this part of Virginia. It is my understanding that 15 percent ethanol is not as good for fuel economy in general but digging around, I am reading that folks in Gen 2s have been running it with no notable difference in fuel economy. Does anyone have any information to share on this? I have run 88 on several other vehicles with no issues. Thanks again for the thoughts.
With the mpg peak being 87 octane correct? If that is the case then it makes my decision a little easier. 87 Octane can have more than 10% ethanol and 88 Octane can have less than 15%. I know that is a best case scenario though.
Here in northern Virginia we only have EPA-reformulated gasoline, so there is no effect of octane on MPG. In other parts of the state it is a more complex question. E10 ethanol is considered to be -3% MPG (48.5 vs. 50 MPG) vs. so E15 would be -4.5% MPG (47.8 vs. 50 MPG). But that assumes all else is equal. The density/MPG of the base gasoline can vary about +-7%. In non-RFG areas, you might be able find higher MPG fuels, because in so many words, EPA equates lower density with cleaner burning. If you go back a few years on Prius Chat, I made some density calcs by getting exactly 1.5-gallons of gas and weighing the gas can to get weight and density. However, since I live in a low-density RFG area, with no E0 allowed, I do not have much interesting variation. The other option is to try each fuel and see which gives best MPG, but on a Gen2 Prius that is so hard to tell because MPG is so sensitive to warm-up, flexible "guess" tank, and other factors. I find my new RAV4H seems much less variable MPG than the Gen2 - in other words less MPG debit for short trips. So then, if you go back further on PriusChat, you will see a "thermistor hack" that was semi-popular DIY electronic mod to fake-out the Gen2/3 Prius to make it get out of the cold start/ low MPG mode faster. Keep in mind your Gen2 Prius is a 50-state near-zero-emission car, so it is designed with California in mind, and California is demanding low smog emissions at cold start-up. So that's why Gen2 Prius had to reduce MPG in the cold state, to allow the cat converter to come up to full temp before allowing better MPG. The thermistor hack circumvents some of that cold-start MPG debit. These days there is less interest in maxing Gen2/3 MPG so there is less discussion about thermistor hack. Aside from milking the most MPG, all of the gaso fuels should work fine. Gen2 is probably designed for E10 so for E15 you could void the 2005 warranty. Other popular +MPG options were engine block heater rod, which is common in northern climates especially in winter. Also blocking the air vents to the radiator. Of course, if you have an attached garage that is a little warmer in winter, that is big help too.
NO. You are mixing apples and oranges. Octane does NOT indicate the amount of ethanol. Two different things. Like you said in the first post, most people (regardless of the car) won't notice any significant difference in the mileage with E0 versus E10 even though E0 has about 3% higher energy content.
How much cheaper? If this is just the difference between E10 and E15, then it is a wash if the 88 is priced 1.5% cheaper than the 87.
use 87 or 88 if it is cheaper but has the same or less ethanol. if you prefer and can find it, compare ethanol content vs cost. i do think it is a wash though.
