99 civic EM1 with bad gas mileage?

[Barefoot]

It most certainly can be the ethanol in the gas. The cars computer cannot detect it and it has to add more to get it to maintain the proper fuel ratio. You can get it tuned out but with the ethanol content changing in the gas all the time its hard to keep up with it.

that cant be true. if it was ever car on the road that wasnt flex fuel would be getting bad mpg. i know my stock 91 accord is getting 32 mpg still with the 10% ethanol they add.

[Batlground]

that cant be true. if it was ever car on the road that wasnt flex fuel would be getting bad mpg. i know my stock 91 accord is getting 32 mpg still with the 10% ethanol they add.

Unfortunately, it is true. You may not notice it but that doesn't mean its not happening. Think about it, you need 30% more ethanol than gasoline to maintain the same air fuel ratio. When you add 10% of ethanol to gas the computer has to add 3% more total fuel through the injectors to compensate for the 10% in ethanol. We have tested cars on the dyno from 10% ethanol to 90% ethanol for a special project that we have been working on.