I have a 1995 Integra LS Sedan with a B18B1 and a 5spd man. I used to get 31-33+ MPG on the highway in my car about a year ago, while using the AC. Lately, I've been getting significantly less than that. Last weekend, I got 28.5 mpg on a 275 mile trip. I was only driving 65-75 mph the whole way as well, but it was all highway miles. It was raining hard for 1/4 of the trip and for 1/2 of the trip I was battling a 20-30mph headwind. I also had the AC on for the majority of the trip and had about 500lbs of people, gear and dogs in the car including myself.

Here is a list of things that I've thought about and/or checked: tire pressure 33-37psi, new air filter, tires balanced, wheels aligned, proper oil weight, newer thermostat and radiator and good coolant level, new distributor cap and rotor, good spark plus and wires, no excess weight in the car, valves recently adjusted and timing belt replaced, 90K and 105K tuneup, fuel injector cleaner used a few times a year, new fuel filter. The wheels and tires are new and the tires may add some rolling resistance since they are Kumho "W" rated and have a "AA" rating for traction. The wheels however are very light. They are 15" Konig Feather's and weigh around 11.5-12lbs each.

I know there are a million things that can cause bad mileage, the most important being driving habits. I've thought about the O2 sensor, but Honda doesn't have a recommended replacement time unless there is some sort of trouble code or check engine light triggered. The same went for the fuel filter, but I replaced that myself anyway, since its a cheap part and fairly easy to do. I've even tried to remove the O2 sensor with the special socket from the auto parts stores and I can't seem to get a good leverage point on it with either a wrench or a ratchet without removing the headers from the car all together.

Any ideas anybody? Any help would be great. I've thought about a compression check or power loss, but the car seems to have plenty of power and doesn't feel much weaker than it used to, if at all.

Sorry for the long thread and thanks for any ideas and or help guys!