Freedom of choice: E20 ethanol blends take the value crown from gasoline, E10

Engine performance in the real world

Another difference in the real world is in engine performance. Now, inexplicably there is not a lot of research done on the trade-off in mileage between cars running straight gasoline and various blends of ethanol. It’s common knowledge that ethanol, as a fuel molecule, has a much lower energy density — but there are more factors to consider than strict energy density.

For example, ethanol advocates over the years have hypothesized that extra oxygen available in ethanol-blended fuel can result in a more complete fuel burn — and there have been hypotheses that ethanol blends can boost real-world performance by requiring less fuel to generate power for acceleration.

The EERC study on fuel economy

Fact or fiction? A few years back, the American Coalition for Ethanol put those hypotheses to the test in contracting with 6the Energy & Environmental Research Center at the University of North Dakota for real-world engine testing. It’s one of the few set of tests done which looks at a wide range of ethanol blends, instead of just comparing straight gasoline to E85 ethanol blends.

By the way, here’s the study.

In testing a set of flex-fuel and standard vehicles, the researchers showed that no two vehicles were alike, and no two blends of fuel performed exactly as a straight-line analysis of energy content predicted. A non-flex-fuel Ford Fusion tested by the team had the best cost per mile running e30 blends, which is the car is not even entitled to use under EPA regulations.

By contrast, a flex-fuel Chevrolet Impala had its best cost per mile performance running E20 ethanol — including a shocker of a result that it generated higher mileage running E20 than straight gasoline, even though gasoline has substantially higher energy density. A non-flex-fuel version of the same Chevy Impala — now, get this one — had its best cost per mile performance on E40 blends of ethanol. A non-flex-fuel Toyota had its best results, on a cost per mile basis, running E30 – and in one test generated higher mileage using E30 despite the lower energy density — and despite the fact that you can’t legally use E30 ethanol blends for non-flex-fuel vehicles.

Go figure.

What the data should tell us is that cars are highly differentiated. Not only by their make, model and year — their “genotype”, if you will. But presumably they will have vastly different results based on their real-world driving and maintenance pattern — their “phenotype”, for you biologists.

In today’s Digest, we go in-depth with the data — looking at the impact of regional pricing — and putting it all together into a look at real fuel economy – and the surprising winners – via the page links below.