Interested to find out if anyone else has experienced the following.

The gas mileage on my 1996 Civic EX always comes up to be either of two distinct numbers that are not even close. I frequently make one particular highway trip that produces either 32 MPG or 38 MPG.

I question why the gas mileage number never falls between these values. Buying gas exclusively at the same station does not solve the problem.

What might be causing this?

Could it be caused by an electronic glitch in some computer controled system?

Thanks for any ideas on what to look for to consistently get that 38 MPG number.

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How are you calculating your gas mileage?

You should reset your trip meter at every fill-up and divide your gallons put into your tank into the miles driven for your accurate mileage for the next 3-5 fill-ups.

 

If you are indeed measuring your MPG like ek forever guy suggested, there could be something that is causing your problem.
The ECU injects more fuel when the engine is below temperature. Perhaps your thermostat or temperature sensor is failing and causing you to get poor mileage on some trips. Or, perhaps your MPG numbers are on days with very different temperatures.

 

Maybe you get the higher number in one direction and the lower number in the other because of the elevation changes on the trip?