David mentioned something about it when it came out a couple of months ago, but as Grist wraps up its first week of biofuel coverage, it’s worth pointing to again: after much testing and comparing, Consumer Reports finds the whole live-green-go-yellow, E85 thing pretty much a sham.

As Grist readers will know, the government gives automakers a credit against their mileage requirements for every flex-fuel vehicle (able to run on ethanol, gas, or a mix).

CR’s conclusion: Detroit is using it a lever to help it churn out more gas-guzzling SUVs, and the policy is working to increase fossil fuel consumption, not stem it.

The most depressing finding, for me: the greenwash appears to be sticking with the general public:

A recent Harris Interactive study of vehicle owners found that more than half were interested in purchasing an FFV, mostly for reduced dependency on petroleum and improved fuel economy.

Ouch.

CR shows that, so far, Detroit has focused on SUVs for flex-fuel treatment. Predictably, E85 is a bust from a mileage standpoint, since ethanol has about a third less energy per gallon than gasoline. Worse, E85 is widely available only in the Midwest, particularly Minnesota.

Here’s the kicker:

The FFV surge is being motivated by generous fuel-economy credits that auto-makers get for every FFV they build, even if it never runs on E85. This allows them to pump out more gas-guzzling large SUVs and pickups, which is resulting in the consumption of many times more gallons of gasoline than E85 now replaces.

Note that this analysis is completely independent of the larger question of whether ethanol based on corn, feedstock for 99 percent of the ethanol produced today, has a net positive environmental effect.

Say it did; say corn ethanol were the “renewable fuel” hailed by its champions. The E85/flex fuel thing would still be absurd. Here’s why: All cars available in the U.S. since 1980 have been able to run on gas mixed with up to 10 percent ethanol. The U.S. consumes about 140 billion gallons of gas per year.

Which means that without any dubious mileage incentives — without any equipment modifications, flex-fuel vehicle rollouts, E85 stations — we could consume 14 billion gallons of ethanol. That’s nearly triple the amount the U.S. is expected to consume in 2006.