Major loss in MPG
 

I have a '95 Civic EX with the 1.6 in it. I haven't done really any modifications to it but I have been getting about 38 MPG with it until recently when one tank dropped to about 30 and then went up back up the next tank. It went back and forth a few times and now has stayed low for the last several times. I was getting the same fuel from the same station this whole time. Any ideas on what could make the fuel mileage drop so much like that? Thanks!

sometimes the pump doesn't stop at the same point every time, so if it stops too soon your calculations show you got good MPG, then next time you may fill up more and you get worse MPG..also the winter is killer on fuel economy...

are you idling more than before? and tires low on air? are you still driving the same type of trips as before or are they different?

No, not idling anymore than before, my tire pressure is the same, and my trips have been the same, between home and work, 27 miles one way. I don't drive hard and haven't changed my driving style.

Do you use a mpguino or anything to monitor real time fuel consumption? This would make it easier to see if it is caused by your behavior.

Cold weather has a big impact on fuel economy, especially if you have to let it warm up to get the windows clear enough to drive.

Some mechanical problems can cause increased fuel consumption. A failing O2 sensor is high on the list of the usual suspects.

Any other symptoms you have noticed?

One other thing that I have noticed is the car sort of surging during acceleration. Sort of like I am pumping the throttle even though I'm not. I have wondered if it could be a sensor of some kind.

Cold weather saps 5-8 MPG outta my 04EX for certain. 2 Months ago going cross country, I got 42 MPG at 65°F, the next day, cold front passed over me (ya think?) and it was lower 20's°F with a 20-30MPH headwind kicker, 28MPG. I hate North Dakota.

Surging doesn't sound normal. Could it be a vacuum or fuel delivery issue?

the problem it could be anything...if it's surging something is wrong...it could be the distributor or anything else. take it to a mechanic unless you can diagnose some engine problems

When was the last time the vehicle was serviced? Surging during acceleration is definitely not normal.

Hook up a vacuum gauge. Surging sounds bad