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Ron LambertySeptember 21, 20232 min read

What the HEFF Are We Waiting For?

After California announced its zero emissions vehicle (ZEV) policy in late 2020 - widely understood as a battery electric vehicles (BEV) mandate and internal combustion engine (ICE) ban - ACE began developing our hybrid flex-fuel project to show ZEV conventional wisdom wasn’t very wise. We theorized a standard hybrid EV powered by the lowest CI E85 available (corn fiber ethanol + renewable naphtha) would have a total GHG score around 55 grams of CO2 per mile – about half the national average lifecycle CO2 estimate for a 2019 Tesla Model 3 Long Range (LR).

Our theory was based on U.S. Department of Energy’s calculations, which are notoriously “optimistic,” so, since converting my 2019 Ford Fusion Hybrid to “HEFF,” the hybrid electric flex fuel vehicle, using a conversion kit supplied by, we’ve recorded mileage, gallons, flex fuel cost, and ethanol content at every fill. E10 price is also recorded, and cost calculated based on a benchmark set by driving 3,700 E10 miles before conversion, adjusted for seasonal variations which we confirmed with a few tanks of E10.

After running 25,000 miles on fuel averaging 71 percent ethanol (with zero maintenance issues), using real-world mileage and the average carbon intensity (CI) of ACE ethanol producer members, HEFF emitted about 200 grams per mile (g/m) CO2. Substituting corn-fiber ethanol drops the CI number below 150, and E71 made with the lowest CI components approved by CARB would emit only 70 g/m. If we used E85, the CI numbers would be 185, 119, and 71. Not bad, but not as low as we projected.

Not to worry. It turns out estimates for BEVs aren’t very accurate either. They say the 2019 Tesla 3 LR emits 111 g/m CO2 with 310 miles range per charge, while my unofficial “survey” of two 2019 Tesla 3 LR Uber drivers reported 210 to 240 miles per charge. Fortunately, I can back up my random anecdotal estimates with Car and Driver’s 40,000-mile road test, placing Tesla’s range 80 miles below the 310 estimate. That 26 percent difference changes Tesla’s 111 g/m U.S. average CI to 146 g/m - almost identical to HEFF running on corn fiber ethanol flex fuel, and twice the CO2 of HEFF using the lowest CI flex fuel. Tesla only matches the lowest CI flex fuel in the cleanest U.S. electric markets where the adjusted CI becomes 72 grams CO2 per mile.

And so far, all that carbon reduction has saved us $219 bucks versus running the same miles on E10.

If folks are serious about reducing carbon pollution, what the HEFF are they waiting for?