Massachusetts has switched to E10 ethanol gas (gasohol) everywhere, and my 02 civic EX makes terrible mileage on it.

My wife just drove back from NJ and made 38mpg on the highway on NJ gas. On MA gas with 90% highway driving she makes like 28mpg. Now, I know that ethanol has less BTUs/gal and E10 should drop milage by 1-3%, but this is rediculous!

My dealership told me the car was fine a few months ago, but with this NJ trip, it's clear that something is wrong with the car.

I'm thinking O2 sensor, but I'm looking for confirmation or other ideas. If the O2 were far off, it's supposed to throw a CEL.

Thoughts?

 

I didn't realize you could run ethanol in a car designed only for gasoline.

Ethanol burns a lot different so I would assume different ignition tuning would be necessary.

 

its only 10% ethanol, so the ecu can adjust for it.

 

Oh, I thought he was talking about straight ethanol...

I use that blend and my car runs fine.

 

Yeah, its when you run E18 you have to modify your **** so it can run it.

As far as the ****ty gas milage, not quite sure. Only thing that i can think of is injectors need cleaned, but being an 02 you would think they were ok. not really sure mang.

 

Maybe there's some vapor locking in the injector thats messing with the injectors.. only problem is that VP usually kills an engine due to lack of fuel so there might be other things going on in conjunction with that which cause worse mileage.