Low Mileage With Ethanol

For the past several months (even before the fuel prices started skyrocketing), we've been using Shell's E-10 Ethanol Blend for our Altis and CRV. E-10 was PHP2.00 cheaper than regular unleaded (although its now just PHP1.75 cheaper) and according to people I've talked to, modern cars with fuel-injected engines should have no problem with ethanol. At some point during the peak of the fuel crisis, all gas stations would run out of E-10 as everyone switched to it.

I saw Petron's ad recently claiming that their Extra Unleaded gasoline gives better mileage to cars. That made me wonder whether there is really a difference in terms of mileage depending on what kind of fuel you use. So I had both CRV and Altis driven until their tanks were empty then filled them up with E-10 so I can measure their mileage. The CRV has a 48L tank and the Altis has 40L.

After about a week and a half, both tanks were already empty. We checked the odometer and were surprised with the finding. The last time I measured their mileage was a couple of years ago when we were still exclusively using unleaded fuel. Back then, the Altis does about 11 km/liter, while the CRV does about 9 km/liter. With this recent experiment, the Altis showed a dismal 8 km/liter, and the CRV just below 6 km/liter! A drop of more than 25% in terms of mileage! For a measly 4% to 5% savings on E-10 vs. Unleaded, we lost 25% in mileage.

Could this have been just coincidental or does E-10 really evaporate faster, and thus, get consumed faster than regular unleaded? Well, we emptied both tanks again today and filled them up with regular unleaded. Odometers have been reset to zero, so we'll see in a couple of week's time if mileage improves with regular unleaded.