Sunday on the way home from Belmont we stopped in Pontotoc for some cheap gas ($3.40 to be exact). There was a sticker on the pump that said “Enriched with Ethanol.” Someone had taken the liberty to cross out “Enriched” and had replaced it with “Diluted.” While I deplore vandalism, I was a little amused that someone felt so strongly about the situation.
I had previously heard claims (on the local talk radio station) that gasoline with ethanol added gave you worse gas mileage than straight gasoline. I had never given it much thought, but the vandalism made me curious.
The most definitive numbers I could find were in a report from the American Petroleum Institute (page 9). The API is a trade association for the US oil industry, so, if anything, you would expect their numbers to err on the negative side. The report cites a small study using 2001-2003 model year cars and light trucks that shows a 1.4% fuel economy penalty when using fuel with 10% ethanol, the most common mixture. They cite another study using older cars (1989 models) that shows a 2.6% fuel economy penalty.
Let’s use the number for more recent cars: 1.4%. That means if your car gets 25 mpg with regular gasoline, it’ll get 24.65 mpg with 10% ethanol. That doesn’t sound like a big difference, but if regular gasoline is being sold for $3.59 a gallon then gasoline with 10% ethanol would have to be $3.54 or cheaper to make up for the decrease in fuel efficiency. So, keep this in mind and buy your gas accordingly.
Of course, if the US taxpayer wasn’t subsidizing the production of ethanol then this wouldn’t be an issue, but I digress. That is, perhaps, a blog post for another day.